U.S. patent application number 12/023056 was filed with the patent office on 2008-10-02 for radio communication method, radio mobile device and radio base station accommodation apparatus.
Invention is credited to Shiro Mazawa, Yosuke TAKAHASHI, Daigo Takayanagi, Akihiko Yoshida.
Application Number | 20080242303 12/023056 |
Document ID | / |
Family ID | 39795316 |
Filed Date | 2008-10-02 |
United States Patent
Application |
20080242303 |
Kind Code |
A1 |
TAKAHASHI; Yosuke ; et
al. |
October 2, 2008 |
RADIO COMMUNICATION METHOD, RADIO MOBILE DEVICE AND RADIO BASE
STATION ACCOMMODATION APPARATUS
Abstract
In a radio communication system in which sequence numbers of
radio packets transmitted to first and second radio base stations
are managed independently to perform hand-off, when the hand-off is
performed while a plurality of fragmented radio packets are
transmitted, a mobile device applies sequence numbers of radio
packets managed by the first radio base station after the hand-off
is performed and applies sequence numbers of radio packets managed
by the second radio base station after completion of transmission
of the plurality of radio packets. The radio base station managing
radio packets is identified on the basis of the sequence numbers
managed in each base station upon restoration and data is
restored.
Inventors: |
TAKAHASHI; Yosuke;
(Yokohama, JP) ; Yoshida; Akihiko; (Yokohama,
JP) ; Takayanagi; Daigo; (Yokohama, JP) ;
Mazawa; Shiro; (Fujisawa, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET, SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
39795316 |
Appl. No.: |
12/023056 |
Filed: |
January 31, 2008 |
Current U.S.
Class: |
455/436 |
Current CPC
Class: |
H04W 36/08 20130101;
H04W 36/02 20130101; H04W 92/045 20130101 |
Class at
Publication: |
455/436 |
International
Class: |
H04Q 7/20 20060101
H04Q007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 26, 2007 |
JP |
2007-078138 |
Claims
1. A radio communication method 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, comprising: making the radio mobile device control
to apply, when the hand-off is performed while the radio mobile
device subjects transmission data to fragmentation to divide the
transmission data into a plurality of radio packets and transmits
the plurality of radio packets, 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 making the radio base station accommodation apparatus
identify a radio base station managing radio packets on the basis
of the sequence numbers managed in each radio base station and
restore data for each radio base station.
2. A radio communication method according to claim 1, wherein the
hand-off is performed by a method using Route Selection Protocol
(RSP).
3. A radio communication method according to claim 2, wherein
management of the sequence numbers of radio packets in the radio
base station is performed using Radio Link Protocol (RLP).
4. A radio mobile device 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, comprising: a radio transmitter-receiver part, a
modulator-demodulator circuit, a control part and a memory part;
the control part controlling 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.
5. A radio mobile device according to claim 4, wherein the hand-off
is performed by a method using Route Selection Protocol (RSP).
6. A radio mobile device according to claim 5, wherein management
of the sequence numbers of radio packets in the radio base station
is performed using Radio Link Protocol (RLP).
7. A radio base station accommodation apparatus 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, comprising: a communication
interface, a control part and a memory part; the control part
identifying a radio base station managing radio packets on the
basis of the sequence numbers managed independently and restoring
data for each radio base station.
8. A radio base station accommodation apparatus according to claim
7, wherein the hand-off is performed by a method using Route
Selection Protocol (RSP).
9. A radio base station accommodation apparatus according to claim
8, wherein management of the sequence numbers of radio packets in
the radio base station is performed using Radio Link Protocol
(RLP).
Description
INCORPORATION BY REFERENCE
[0001] 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.
BACKGROUND OF THE INVENTION
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
SUMMARY OF THE INVENTION
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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,
[0012] 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
[0013] 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.
[0014] 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.
[0015] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic diagram illustrating the whole
configuration of 1xEV-DO system to which the present invention is
applied;
[0017] FIG. 2 is a diagram illustrating protocol stacks of
transmission data in an embodiment of the present invention;
[0018] FIG. 3 is a diagram illustrating transfer processing of up
packet in an access terminal (AT);
[0019] FIG. 4 is a diagram illustrating receiving and transfer
processing of packet in an access network (AN);
[0020] FIG. 5 is a diagram illustrating receiving and transmitting
processing of packet in PDSN;
[0021] FIG. 6 is a diagram illustrating receiving processing in an
application server;
[0022] FIG. 7 is a sequence diagram illustrating hand-off
processing in a prior art;
[0023] FIG. 8 is a sequence diagram illustrating hand-off
processing when RSP is applied;
[0024] FIG. 9 is a diagram illustrating a flow of data upon change
of up route;
[0025] FIG. 10 is a sequence diagram illustrating a problem upon
change of up route;
[0026] FIG. 11 is a schematic diagram illustrating hardware
configuration of AT in an embodiment of the present invention;
[0027] FIG. 12 is a sequence diagram illustrating a flow of data
after AT transmission control in an embodiment of the present
invention;
[0028] FIG. 13 is a flow chart showing transmission control in AT
in an embodiment of the present invention;
[0029] FIG. 14 is a flow chart showing receiving control in PDSN in
an embodiment of the present invention; and
[0030] FIG. 15 is a schematic diagram illustrating hardware
configuration of PDSN in an embodiment of the present
invention.
DESCRIPTION OF THE EMBODIMENTS
[0031] There is described an embodiment of the present invention to
which a hand-off method to which RSP according to the present
invention is applied in 1xEV-DO network is applied.
[0032] FIG. 1 schematically illustrates the whole configuration of
CDMA 2000 1xEV-DO network to which the present invention is
applied. An access terminal (AT) 101 is communicating with access
networks (AN) 102 and 103. The AN1 and AN2 can each receive radio
waves from AT and can restore packet data transmitted from AT.
Furthermore, AN1 and AN2 transmit the restored packet to PDSN 104.
PDSN 104 transmits the packet received from AN1 (102) or AN2 (103)
through IP (Internet Protocol) core network 105 to an application
server 106. In this manner, data communication between AT 101 and
application server 106 is realized.
[0033] In the above description, AT corresponds to a radio mobile
device, ANs radio base stations and PSDN a radio base station
accommodation apparatus.
[0034] FIG. 2 shows protocol stacks applied to data transmission
from the mobile device to the application server. More
particularly, FIG. 2 shows the protocol stacks applied when data is
transmitted from AT 101 to the application server 106.
[0035] When an application 201 of AT 101 transmits data, IP packet
is produced by IP stack 202 and is framed by HDLC like framing
stack 203. The framed packet is fragmented into a plurality of
packets having the packet size suitable for radio transmission by
means of RLP layer 204 and the packets are assigned sequence
numbers and the like. The packets are radio-modulated by radio
L1/L2 layer 205 to be transmitted to AN1 (102) or AN2 (103).
[0036] Radio waves transmitted from AT are received and demodulated
by radio L1/L2 layer 207 in AN1 (102) or AN2 (103) and RLP packets
are delivered to RLP layer 206. The packets are GRE-capsuled by
GRE/IP layer 208 and transmitted to PDSN 104 by Ethernet
(trademark) 209.
[0037] PDSN 104 decapsules GRE/IP packets received by Ethernet 213
by means of GRE/IP layer 212 and delivers the packets to HDLC like
framing layer 211. The packets are deframed in HDLC like framing
layer 211 and delivered to IP layer 210. The IP packets are
transmitted to the application server 106 by IP layer 214 using
Ethernet 215. The packets received by Ethernet 218 of application
server 106 are processed by IP layer 217 to be delivered to the
application 216.
[0038] FIG. 3 is a diagram illustrating transfer processing of up
packets transmitted from AT.
[0039] Application data 301 produced by application 201 is
delivered to IP; layer 202. The data is assigned IP header 302 in
IP; layer 202 and is then delivered to HDLC like framing layer 203.
The data is assigned header 303 and trailer 305 in HDLC like
framing layer and is then framed to be delivered to RLP layer 204.
The data is fragmented to have the data size suitable for radio
transmission in RLP layer 204. In FIG. 3, the data received from
HDLC like framing layer is divided into two RLP packets. That is,
the data is divided into two RLP packets including one having RLP
header 306 and data 307 and the other having RLP header 308 and
data 309. Both of RLP packets are delivered to radio L1/L2 (layer
1/layer 2) 205 and assigned radio headers 310 and 312,
respectively, to be transmitted to AN.
[0040] FIG. 4 is a diagram illustrating processing for transmitting
data received from AT in AN to PDSN.
[0041] When radio L1/L2 207 receives the radio packets from AT, the
radio L1/L2 removes radio headers 401 and 403 therefrom and
delivers the packets to RLP layer 206. RLP layer 206 removes RLP
headers 405 and 407 from the packets and delivers the packets to
GRE/IP layer 208. GRE/IP layer 208 assigns GRE/IP headers 409 and
411 to the packets and Ethernet layer 209 assigns Ethernet headers
413 and 415 thereto to be transmitted to PDSN.
[0042] FIG. 5 is a diagram illustrating processing for transmitting
data received from AN in PDSN to the application server.
[0043] When Ethernet layer 213 receives the data from AN, the
Ethernet layer removes Ethernet headers 501 and 503 therefrom and
delivers the data to GRE/IP layer 212. GRE/IP layer 212 removes
GRE/IP headers 505 and 507 from the data and delivers the data to
HDLC like framing layer 211. HDLC like framing layer 211 combines
packets divided plurally to restore one packet composed of header
part 509, IP packet part 510 and trailer part 511. The packet is
delivered to IP layers 210 and 214 and further delivered to
Ethernet layer 215. In Ethernet layer 215, the packet is assigned
Ethernet header 514 to be transmitted to the application
server.
[0044] FIG. 6 is a diagram illustrating processing for delivering
data received from PDSN in the application server to the
application.
[0045] Ethernet header 601 of the packet received from PDSN is
removed in Ethernet layer 218 and the packet is delivered to IP
layer 217. IP layer 217 removes IP header 603 therefrom to be
delivered to the application 216.
[0046] As shown in FIGS. 3 to 6, data transmitted from AT to the
application server is framed by HDLC like framing and is then
divided into the plurality of packets in order to produce RLP
packets suitable for radio transmission. The divided packets are
combined by HDLC like framing of PDSN to be transmitted to the
application of the application server finally.
[0047] FIG. 7 is a sequence diagram illustrating processing of a
hand-off method in a prior art.
[0048] FIG. 7 shows the processing in case where AT is moved from
AN1 to AN2. Down data transmitted from application server to AT is
first transmitted from application server to PDSN (701) and then
transmitted from PDSN to AN1 (702) and finally transmitted from AN1
to AT (703). In up data transmitted from AT to application server,
data transmitted from AT is first received by both of AN1 and AN2
(704, 705). Since AN1 is an anchor AN which terminates down data,
AN1 transmits data received from AT to PDSN (706). Data 705
received by AN2 from AT is generally transferred to AN1 for the
purpose of upward selection and combination, although omitted in
the drawing. AN2 does not transmit data to PDSN.
[0049] In such situation, the hand-off for making the AT receive
down data from AN2 is performed. At this time, AT transmits a
control signal named Data Rate Control (DRC) to AN1 (708). The DRC
contains information indicating AN2 as down-data transmission
change destination. AN1 stops packet transmission processing for
both of down data and up data (709). The reason thereof is that the
sequence number of data (RLP packet) transmitted from AN1 to AT and
the sequence number of data (RLP packet) transmitted from AT to AN1
are required to be taken over to AN2 and when data processing is
performed during taking over, the sequence number being used by AT
does not coincide with the sequence number to be used by AN2. AN1
transmits a hand-off request signal to AN2 in order to change the
flow of data to AN2 (710). The hand-off request signal contains the
sequence numbers of RLP packets used by AT and AN1. AN2 transmits
the hand-off request signal to PDSN (711) to request PDSN to change
the down data transmission destination from AN1 to AN2. PDSN
transmits a hand-off response signal to AN2 and informs AN2 that
the hand-off request signal is processed normally and down data is
started to be transmitted to AN2. AN2 transmits a hand-off response
to AN1 (713) and informs AN1 that hand-off receiving preparation
has been arranged. AN2 uses RLP sequence number received from AN1
to complete preparation for data transfer and resumes the packet
transfer processing (714).
[0050] By performing the above processing, the down data 715
transmitted from application server to PDSN is transmitted through
PDSN to AN2 (716) and further transmitted to AT by radio (717). The
up data transmitted from AT is received by AN1 and AN2 (718, 719).
Since AN2 is an anchor AN which terminates the down data, AN2
transmits data received from AT to PDSN (720). The data 718
received by AN1 from AT is generally transferred to AN2 for the
purpose of upward selection and combination, although omitted in
the drawing. AN1 does not transmit data to PDSN.
[0051] As described above, since the hand-off method in the prior
art requires to take over the RLP sequence numbers when the
hand-off is performed, data communication cannot be made during
taking over of data, so that a stop period of packet transfer
processing occurs. Consequently, delay and jitter occur due to it
and a large problem arises in case where an application of a
real-time system such as particularly VoIP is processed.
[0052] FIG. 8 is a sequence diagram illustrating a flow of
processing of the hand-off method in case where RSP is applied
thereto.
[0053] FIG. 8 shows an example of the processing in case where AT
is moved from AN1 to AN2.
[0054] In this processing, RSP is applied and it is supposed that
AN1 of hand-off source manages RLP by Route A and AN2 of hand-off
destination manages RLP by Route B. RLPs in the respective routes
manage the sequence numbers independently and accordingly even when
the hand-off is performed, it is not necessary to take over the
sequence numbers. Down data from the application server to AT is
first transmitted from the application server to PDSN (801), then
transmitted from PDSN to AN1 (802) and finally transmitted from AN1
to AT (803).
[0055] Since AN1 manages RLP by Route A, the RLP packet transmitted
from AN1 to AT indicates that it is a packet for Route A. In up
data transmitted from AT to the application server, data
transmitted from AT is received by both of AN1 and AN2 (804, 805).
Since data transmitted from AT is being in communication using
Route A, the data contains information indicating that it is packet
for Route A. Since AN1 which has received the packet for Route A
recognizes that it is packet data for Route managed by AN1 itself,
that is, packet for Route A, AN1 receives the data and transmits
the data to PDSN (806). On the other hand, similarly, AN2 also
receives packet for Route A from AT, although since it is not
packet data for Route managed by AN2 itself, that is, packet for
Route B, AN2 does not transmit the received data to PDSN and annuls
it. PDSN transmits data 806 received from AN1 to the application
server (807).
[0056] In such situation, the hand-off for making AT receive down
data from AN2 is performed. At this time, AT transmits a control
signal named Data Rate Control (DRC) to AN1 (808). DRC contains
information indicating AN2 as down-data transmission change
destination. The hand-off to which RSP is applied is different from
the hand-off to which RSP is not applied as described in FIG. 7 and
is not required to stop packet transmission processing of up data
and down data. The reason thereof is that RLPs for hand-off source
and hand-off destination can be operated independently by RSP and
it is not necessary to take over the sequence numbers. Accordingly,
AN1 transmits a route change request (809) to AN2 without
interrupting data transmission processing. AN2 transmits the route
change request (810) to PDSN and requires to change down-data
transmission destination from AN1 to AN2. PDSN changes the
down-data transmission destination to AN2 in response to the
request.
[0057] After this, down data 811 from the application server
transmits to AN2 through PDSN (812). The data is further
transmitted from AN2 to AT (813). Since AN2 manages RLP by Route B,
RLP packet transmitted from AN2 to AT indicates that it is packet
for Route B. When AT receives the packet for Route B, AT changes
the route so that up data transmitted from AT to AN also uses
packet for Route B. The up data transmitted from AT is received by
AN1 and AN2 (814, 815). Data transmitted from AT contains
information indicating that it is packet for Route B since the data
is being in communication using Route B. Since AN2 which has
received the packet for Route B understands that the received
packet is packet data for Route managed by AN2 itself, that is,
packet for Route B, AN2 performs receiving processing and transmits
the data to PDSN (816). On the other hand, AN1 also receives the
packet for Route B from AT similarly, although since the received
packet is not packet data for Route managed by AN1 itself, that is,
packet for Route A, the received data is not transmitted to PDSN
and is annulled. PDSN transmits data 816 received from AN2 to the
application server (817).
[0058] FIG. 9 is a sequence diagram illustrating a problem which
can arise upon route change of up transmission data in the hand-off
to which RSP is applied.
[0059] In this example, AN1 manages RLP by Route A and AN2 manages
RLP by Route B. Furthermore, the case where the transmission delay
between PDSN and AN1 is longer than that between PDSN and AN2 is
shown. On such conditions, the procedure of performing the hand-off
for changing a data communication route to AN2 during communication
between AT and AN1 is now described.
[0060] Down data 901 transmitted from the application server is
received by PDSN and then transmitted to AN1 (902). With regard to
data 902 transmitted from PDSN to AN1, the drawing shows that the
transmission delay between PDSN and AN1 is large and accordingly it
takes delay to receive the data by AN1 after the data is
transmitted by PDSN. Since AN1 is the base station which manages
Route A, AN1 produces packet for Route A and transmits it to AT
(903). Since AT receives packet for Route A from down data, AT
transmits packet for the same Route A even in the up direction when
the AT transmits up data. It is supposed that one packet produced
by application of AT is divided into two RLP packets to be
transmitted to AN1. In other words, two data 904 and 905 constitute
one IP packet and are assigned sequence numbers 1 and 2,
respectively, as RLP packets for Route A to be transmitted to AN1.
When AN1 receives the packets, AN1 transmits the packets to PDSN
(906, 907). When PDSN receives the two packets 906 and 907, the
packets are deframed by HDLC like framing to produce one IP packet
and PDSN transmits data to the application server (908).
[0061] Similarly, AT divides one packet produced by application
into two RLP packets and starts to transmit the packets to AN1,
although it is supposed that the hand-off for changing to Route B
is performed when only one of the two packets is transmitted.
Accordingly, when AT transmits the first packet of two RLP packets
produced from one packet produced by application as packet for
Route A (909), the hand-off for changing to Route B is performed
and down packet 911 from the application server is transmitted
through PDSN to AN2 (912) and packet for Route B is transmitted to
AT (913). When AT receives the packet, AT transmits up data as
packet for Route B (914). The first RLP packet produced from one
packet is transmitted to AN1 and further transmitted to PDSN (910).
The packet arrives at PDSN late due to the transmission delay
produced between AN1 and PDSN.
[0062] On the other hand, the second RLP packet is transmitted to
AN2 and further transmitted to PDSN (915). PDSN receives the packet
915 from AN2 and the packet 910 from AN1 in order of description
and accordingly PDSN cannot make deframing by HDLC like framing
normally, so that PDSN annuls the packets.
[0063] FIG. 10 is a diagram illustrating annulment of packets in
PDSN due to change or replacement of packets.
[0064] IP packet (composed of IP header denoted by 1001 and
application data denoted by 1002) produced by AT is subjected to
HDLC like framing, so that header 1003 and trailer 1005 are added
thereto. The packet is fragmented into two RLP packets having the
packet size suitable for radio transmission. The first RLP packet
includes RLP header 1006 and first half part 1007 of data and the
second RLP packet includes RLP header 1008 and second half part
1009 of data.
[0065] When the order of the two RLP packets is changed and GRE/IP
packets arrive at PDSN, packet including GRE header 1010 and second
half part 1011 of data arrives as first GRE/IP packet and packet
including GRE header 1012 and second half part 1013 of data arrives
as second GRE/IP packet.
[0066] In HDLC like framing processing in PDSN, the two packets are
combined, although data is not restored due to change of data order
of packets, so that the packets are annulled.
[0067] FIG. 11 is a schematic diagram illustrating hardware
configuration of AT in an embodiment of the present invention.
[0068] AT 101 includes a central processing unit (CPU) 1101, a
memory 1102 and a clock 103, which are connected to a communication
bus. The CPU 1101 subjects data to be transmitted to production
processing of RLP packet described in the embodiment of the present
invention and the data is once stored in the memory 1102.
Thereafter, the data is read out from the memory by a
modulator-demodulator circuit 1104 and is modulated. After
modulation, the data is converted into radio data by an RF circuit
and is transmitted to AN.
[0069] FIG. 12 is a sequence diagram illustrating a flow of data in
case where transmission control of the present invention is
performed.
[0070] As shown in FIG. 12, in the present invention, RLP packets
produced from one IP packet are controlled not to spread over
routes and not to be transmitted upon change of route by AT. An
embodiment for preventing annulment of packets in PDSN by making
control as above is now described in detail.
[0071] First, data 1201 transmitted from the application server in
the down direction is transmitted through PDSN to AN1 (1202). AN1
manages RLP by Route A and packet transmitted by AN1 to AT contains
information indicating that it is packet for Route A (1203). AT
receives packet for Route A from down data and accordingly when AT
transmits up data, AT transmits packet for the same Route A even in
the up direction. In the embodiment, it is supposed that one packet
produced by application of AT is divided into two RLP packets to be
transmitted to AN1. That is, it is supposed that two data 1204 and
1206 constitute one IP packet and the two data are assigned
sequence numbers 1 and 2, respectively, as RLP packets for Route A
to be transmitted to AN1. When AN1 receives the packets, AN1
transmits the packets to PDSN (1205, 1207). When PDSN receives the
two packets 1205 and 1207, PDSN subjects the packets to deframing
by HDLC like framing to produce one IP packet and transmits the
data to the application server (1208).
[0072] Similarly, AT divides one packet produced by application
into two RLP packets to be transmitted to AN1, although when only
one of the two packets has been transmitted, the hand-off for
changing to Route B is performed and down packet 1211 from the
application server is transmitted through PDSN to AN2 (1212), so
that packet for Route B arrives at AT (1213). Accordingly, first
RLP packet produced from one packet is transmitted to AN1 (1209)
and further transmitted to PDSN (1210). It takes time for the
packet to reach PDSN due to the transmission delay occurring
between AN1 and PDSN. In this connection, in the prior art method,
the second RLP packet 1214 is transmitted to AN2 as packet for
Route B since change to Route B has been made, although the packet
1214 is transmitted to AN1 as packet for Route A. This packet is
transmitted from AN1 to PDSN (1215). It also takes time for the
packet 1215 to reach PDSN due to the transmission delay occurring
between AN1 and PDSN.
[0073] After transmission of the packet 1214, when AT transmits
next IP packet, AT transmits the packet using changed Route B. That
is, two RLP packets 1216 and 1218 produced from one IP packet are
transmitted to AN2 as packets for Route B. When the transmission
delay between AN2 and PDSN is short, the packets reach PDSN
immediately (1217, 1219).
[0074] PDSN receives packet 1210 from AN1, packet 1217 from AN2,
packet 1219 from AN2 and packet 1215 from AN1 in order of
description, although the packets are subjected to deframing
processing by HDLC like framing for each AN, so that IP packet can
be restored from packets 1210 and 1215 to be transmitted to the
application server as data 1221. Furthermore, IP packet can be also
restored from packets 1217 and 1219 to be transmitted to the
application server as data 1220. At this time, the transmission
order of the packets 1220 and 1221 is different from the order of
production in AT, although reversal of the order can be processed
properly by the application server because of change or replacement
of IP packet unit.
[0075] FIG. 13 is a flow chart showing transmission control of AT
in the present invention. When AT receives down data (1301), AT
confirms route which is applied currently (1302). When the route
applied currently is Route A and the received packet is Route B
(1303), the applied route is changed to Route B (1304). When the
received packet is Route A, the applied route is left to be Route
A. When the route applied currently is Route B and the received
packet is Route A (1305), the applied route is changed to Route A
(1306). When the received packet is Route B, the applied route is
left to be Route B.
[0076] In such state, when there is up transmission data (1307),
the transmission IP packet is subjected to HDLC like framing (1308)
and RLP packets are produced by the current applied route (1309).
All the RLP packets produced from one transmission packet are
transmitted using the same route (1310).
[0077] FIG. 14 is a flow chart showing receiving control in PDSN in
the present invention.
[0078] When PDSN receives up data (1401), PDSN judges route of the
received packet (1402). The route is judged on the basis of whether
the packet is received from the AN for Route A or B. When the
packet for Route A is received, the packet is subjected to
deframing by HDLC like framing for Route A (1403). When the packet
for Route B is received, the packet is subjected to deframing by
HDLC like framing for Route B (1404). When restoration of the
respective IP packets is completed (1405, 1406), the restored IP
packets are transmitted to the application server (1407, 1408).
When restoration of IP packets is not completed, the packets are
not transmitted to the application server and PDSN waits for packet
to be received.
[0079] FIG. 15 is a schematic diagram illustrating hardware
configuration of PDSN in an embodiment of the present invention.
PDSN 104 includes a central processing unit (CPU) 1501, a memory
1502 and a clock 1503, which are connected to a communication bus.
Data to be transmitted and received from other devices is subjected
to packet production processing of the present invention by CPU
1501 and once stored in memory 1502. Then, the data is transmitted
through a network interface (I/F) 1504 to the application server or
AN.
[0080] It should be further understood by those skilled in the art
that although the foregoing description has been made on
embodiments of the invention, the invention is not limited thereto
and various changes and modifications may be made without departing
from the spirit of the invention and the scope of the appended
claims.
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