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PCT 



WORLD INTELLECTUAL PROPERTY ORGANIZATION 
~ International Bureau 




INTERNATIONAL APPLICATIO N PUBLISHED UNDER THE PA TENT COOPERATION TREATY (PCT) 

(11) Internationa! Publication Number: WO 99/50974 

7 October 1999 (07.10.99) 



(51) International Patent Classification 6 
H04B 7A4 



Al 



(43) International Publication Date: 



(21) International Application Number: PCT/US99/02429 

(22) International Filing Date: 4 February 1999 (04.02.99) 



(30) Priority Data: 
09/050,240 



30 March 1998 (30.03.98) 



US 



(71) Applicant: MOTOROLA INC. [US/US]; 1303 East Algonquin 

Road, Schaumburg, IL 60196 (US). 

(72) Inventors: GILCHRIST. Philip; Keplerstrasse 17, O-60318 
Frankfurt (DE). GUPTA, Sanjay; Apartment 1 6720 N. 
Lakewood Avenue, Chicago, IL 60626 (US). LADDEN. 
Gregory C; 339 Barn Swallow Lane, Vernon Hills. IL 
60061 (US). SPEAR. Stephen; 25 Williamsburg, Skokie. 
IL 60203 (US). 

(74) Agents: MACINTYRE, John, B. et al.; Motorola Inc., Intellec- 
tual Property Dept., 1303 East Algonquin Road, Schaum- 
burg, II 60196 (US). 



(81) Designated States: European patent (AT, BE, CH, CY, DE, 
DKTES,n,FR,GB,GR,IE,IT,LU.MC.NL,PT,SE). 



Published 

With international search report. 



(54) Title: METHOD FOR ROUTING DATA IN A COMMUNICATION SYSTEM 



sys-Gusc 

SMS-HMSC 




J 1 SM-SC | 



6d V 



115 



101 





HAP-F 



100 



(57) Abstract 

The present invention provides a method for routing data from a service request in a con^^on ^^^^^ 
from a oacket data gateway, such as a Serving GPRS (GSM Packet Radio Service) Support Node (SGSN) (104), to a Base s ^° n ^«m 
JX) context seines where data for this user should be sent The service request is routed to an appropriate 

location, based at least in pan upon the context 



OMCVVin rf-W^ OGPr>C74Al I > 



FOR THE PURPOSES OF INFORMATION ONLY 
Codes used to identify States party to the PCT on the front pages of pamphlets publishing international applications under the PCT. 



AL 


Albania 


ES 


Spain 


AM 


Armenia 


FI 


Finland 


AT 


Austria 


FR 


France 


AU 


Australia 


GA 


Gabon 


AZ 


Azerbaijan 


GB 


United Kingdom 


BA 


Bosnia and Herzegovina 


GE 


Georgia 


BB 


Barbados 


GH 


Ghana 


BE 


Belgium 


GN 


Guinea 


BF 


Burkina Faso 


GR 


Greece 


BG 


Bulgaria 


HU 


Hungary 


BJ 


Benin 


IE 


Ireland 


BR 


Brazil 


IL 


Israel 


BY 


Belarus 


IS 


Iceland 


CA 


Canada 


IT 


Italy 


CF 


Central African Republic 


JP 


Japan 


CC 


Congo 


KE 


Kenya 


CH 


Switzerland 


KG 


Kyrgyzsun 


CI 


Coted'Ivoire 


KP 


Democratic People's 


CM 


Cameroon 




Republic of Korea 


CN 


China 


KR 


Republic of Korea 


cu 


Cuba 


KZ 


Kazakstan 


cz 


Czech Republic 


LC 


Saint Lucia 


DE 


Germany 


U 


Liechtenstein 


DK 


Denmark 


LK 


Sri Lanka 


EE 


Estonia 


LR 


Liberia 



LS 

LT 

LU 

LV 

MC 

MD 

MG 

MK 

ML 

MN 

MR 

MW 

MX 

NE 

NL 

NO 

NZ 

PL 

PT 

RO 

RU 



SG 



Lesotho 
Lithuania 
Luxembourg 
Latvia 



Republic of Moldova 



The former Yugoslav 
Republic of Macedonia 
Mali 

Mongolia 

Mauritania 

Malawi 

Mexico 

Niger 

Netherlands 
Norway 
New Zealand 



Portugal 



Russian Federation 
Sudan 
Sweden 
Singapore 



SI 


Slovenia 


SK 


Slovakia 


SN 


Senegal 


SZ 


Swaziland 


TD 


Chad 


TG 


Togo 


TJ 


Tajikistan 


TM 


Turkmenistan 


TR 


Turkey 


TT 


Trinidad and Tobago 


UA 


Ukraine 


UG 


Uganda 


US 


United States of America 


UZ 


Uzbekistan 


VN 


Viet Nam 


YU 


Yugoslavia 


ZW 


Zimbabwe 



a*jcrvY»irv -WO 0050074A1 I > 



WO 99/50974 



PCTAJS99/02429 



-1- 



METHOD FOR ROUTING DATA 
IN A COMMUNICATION SYSTEM 



Field of the Invention 



10 



The present invention relates generally to 
communication systems, and more particularly to a 
method for routing data in a communication system. 



Background of the Invention 



Typical corporate communication systems include a 
15 wireline networking infrastructure and an in-building 

wireless infrastructure. The wireline networking 
infrastructure is typically packet switched. One 
example of a corporate communication system is a Group 
Special Mobile (GSM) /GSM Packet Radio Service (GPRS) 
20 network. A packet cellular network infrastructure 

consists of a Base Station System (BSS) and Packet 
Support Nodes (PSN) . Currently, a service request is 
placed at the PSN by a mobile station. Thereafter, the 
BSS receives data from the service request from the MS 
25 and forwards it to the Serving GPRS Support Node 

(SGSN) . The SGSN routes the data towards the 
destination. 

Similarly, the PSN forwards any data received for 
a mobile station to the BSS. The BSS sends the data to 
30 the mobile station. Data from a service request 

between a mobile station and a fixed station, 
irrespective of their relative locations, is routed via 
the BSS, the PSN, and one or more wireline gateways. A 



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PCT/US99/02429 



similar procedure is used to route data between mobile 
stations. 

This system satisfies the need for wireless 
telephony and wireless data services. In this system, 
traffic between mobile stations, such as cellular 
telephones, and wireline hosts belonging to the same 
corporate or in-building environment is routed through 
the corporate gateway, one or more GPRS Serving Nodes 
(GSNs), and the Packet Control Unit (PCU) - This 
routing increases end-to-end delays and packet loss and 
can lead to poor utilization of expensive transmission 
resources . 

For mobile station-originated data packets in a 
standardized GPRS system, the BSS does not know the 
destination of the data packets or the ciphering keys 
required to decrypt the data contained in the packets. 
The BSS does not typically know the Temporary Logical 
Link Identifier (TLLI) to Packet Data Protocol (PDP) 
address mapping, such as the IP address or X.25 
address . 

The current approach for handling Circuit Switched 
data for in-building applications is to use the GSM 
recommendations as is, with no special Local Routing 
capabilities. Consequently, an in-building Circuit 
Switched data call will be routed up to the MSC and use 
its InterWorking Function (IWF) . Unless special trunk 
provisioning is performed at the MSC, the Circuit 
Switched data call will be routed through the PSTN to 
the in-building PBX for connection to a wired Circuit 
Switched modem or fax modem. This leads to unnecessary 
transmissions of data, which in turn leads to delays in 
reception and inefficient utilization of resources. 



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Consequently, a need exists for a method for 
routing data in a communication system that does not 
increase delays and that fits seamlessly into current 
communication systems. 



Brief Description of the Drawings 

FIG. 1 depicts a GPRS network in accordance with 
10 the preferred embodiment of the present invention; 

FIG. 2 depicts a layered transmission protocol 
architecture of a GPRS network in accordance with the 
preferred embodiment of the present invention; 

FIG. 3 depicts a protocol stack for local mobile 
15 station to non-local station communication in 

accordance with the preferred embodiment of the present 
invention; 

FIG. 4 depicts a protocol stack for a local mobile 
station to local wireline communication in accordance 
20 with the preferred embodiment of the present invention; 

FIG. 5 depicts a flow diagram for routing packets 
from mobile station hosts to wireline hosts in 
accordance with the preferred embodiment of the present 
invention; 

25 FIG. 6 depicts a flow diagram for routing data 

packets from wireline hosts to mobile stations in 
accordance with the preferred embodiment of the present 
invention; 

FIG. 7 depicts a call flow diagram for a mobile 
30 station, BSS, and packet data gateway communication in 

accordance with the preferred embodiment of the present 
invention ; 



avcnrwry „.w^ oocpo74A 1 i > 



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FIG. 8 depicts a communication network in 
accordance with the preferred embodiment of the present 

invention; and 

FIG. 9 depicts a table that includes the contexts 
maintained by the packet data gateway and the BSS in 
accordance with the preferred embodiment of the present 
invention. 



10 



Detailed Description of a Preferred Embodiment 



The present invention provides a method for 
routing data in a communication system. The present 
invention preferably routes user traffic that 
15 originates from a GPRS Mobile Station (MS) that is 

located in a corporate environment to hosts on the 
corporate wireline network without the data traffic 
leaving the corporate environment. The present 
invention additionally routes user traffic that is 
20 destined from the hosts on the corporate wireline 

network to the GPRS Mobile Station without the data 
traffic leaving the corporate environment. As used 
herein, the ability to route data "in-building" will be 
referred to as "Local Routing" of data. Local Routing 
25 refers to the routing of Group Special Mobile (GSM) 

data traffic at the Base Transceiver Station (BTS) 
level or at the Base Station Controller (BSC) level of 
the GSM hierarchy. The data traffic can include voice 
as well as data. In Local Routing, the routing of user 
30 traffic is separated from the call control, which can 

involve the Mobile Switching Center (MSC) and Serving 
GPRS Support Node (SGSN) as defined in the GSM 



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PCT7US99/02429 



standards. Local Routing is achieved by the separation 
of control and traffic handling procedures. 

The present invention can be better understood 
with reference to FIGs. 1-9. FIG. 1 shows the 
architecture of a GSM Packet Radio Service (GPRS) 
network 100 and the defined interfaces. GPRS network 
100 includes a new functional element, the GPRS Serving 
Node (GSN) 101 that includes a GGSN 102 and an SGSN 
104. GSN 101 provides a high-speed packet-switched 
platform, which supports GSM related mobility 
management. GSN 101 communicates with Base Station 
System (BSS) 103 via a standardized Gb interface 105. 
Gb interface 105 provides access rates per user from 
zero to the maximum possible bandwidth. The maximum 
possible bandwidth is currently between about 2048 
kbit/s. offered by G.704, to about 53 Mbit/s, offered 
by a High Speed Serial Interface (HSSI) . In the 
preferred embodiment, a "transport bit pipe" is 
provided by Frame Relay. In an alternate embodiment of 
the present invention, commonly referred to as 
Universal Mobile Telecommunications System (UMTS) phase 
1, Asynchronous Transfer Mode (ATM) may replace Frame 
Relay without effecting higher layer protocols. All 
user data and control information between BSS 103 and 
SGSN 101 are transported over Gb interface 105. 

SGSN 104 is coupled to BSS 103 via Gb interface 
105. SGSN 104 interacts with GGSN 102 via Gn interface 
107. SGSN 104 interacts with MSC/VLR 109 via Gs 
interface 111. SGSN 104 interacts with HLR 113 via Gr 
interface 115. GGSN 102 interacts with external packet 
data networks 115 via Gi interface 117. SGSN 104 
interacts with other PLMN and GGSNs 119 via Gp 
interface 121. 



WO 99/50974 



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PCT/US99/02429 



SGSN 104 interacts with an Equipment Identity 
Register (EIR) 123 via MAP-F 125. SGSN 104 interacts 
with Short Message Service-Gateway MSC (SMS-GMSC) and 
Short Message Service- InterWorking MSC (SMS-IWMSC) 125 
via Gd interface 127. 

Terminal 129 is terminal equipment, such as a 
computer that is interconnected with a mobile terminal, 
such as a cellular phone that includes a Subscriber 
Identity Module (SIM) card or the like. Um 131 is the 
air interface between mobile station 133 and BSS 103. 

FIG. 2 shows the layered transmission protocol 
architecture for GPRS Network 100. In order for a 
mobile station 201 to communicate via GPRS network 100, 
mobile station 201 must first attach to GPRS network 
100. Mobile station 201 accomplishes this by issuing a 
GPRS location update to SGSN 205, causing SGSN 205 to 
interrogate the Home Location Register (HLR) to obtain 
the record associated with mobile station 201. For 
clarity, only an empty SGSN/VLR is described herein. 
It should be readily understood that the present 
invention also applies to SGSN/VLRs that contain user 
records. Further, interrogation of the HLR may be 
avoided if the SGSN 205 has stored the Mobility 
Management context of mobile station 201. GPRS 
authentication and cipher key allocation or 
reallocation may then occur between SGSN 205 and mobile 
station 201. 

If the GPRS location update is successful, mobile 
station 201 may then set up routing contexts for a 
number of Packet Data Protocol (PDP) addresses. This 
is accomplished by issuing a PDP context activation 
request by mobile station 201 to SGSN 205". The PDP 
context activation request preferably includes an IP 



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PCT/US99/02429 



address and the QoS Profile associated with the IP 
address. In an alternate embodiment, the PDP context 
is dynamically allocated and the activation request 
does not include a PDP address. 
5 As used herein, a context refers to information 

that relates to a mobile station or a mobile user. The 
context also includes information relating to a service 
request for a mobile station or a mobile user. The 
context is utilized to process and route data to and 
10 from a mobile station. 

SGSN 205 analyzes the contents of the request and 
sets up a routing context 209 between SGSN 205 and GGSN 
207. SGSN 205 then holds, and relates, two routing 
contexts. The first routing context is an MS-to-SGSN 
15 routing context. The second routing context is an 

SGSN-to-GGSN routing context. Mobile station 201 or a 
remote host may then communicate via GPRS. 

When a packet destined for mobile station 201 
arrives at GGSN 207, GGSN 207 extracts the destination 
20 address of the packet. GGSN 207 then checks the stored 

MS-to-PDP routing contexts to determine if a match can 
be found between the stored contexts and the 
destination address of the packet. If a match is not 
found, the incoming packet is preferably discarded. 
25 Alternately, the incoming packet can be returned to the 

originator of the packet. If a match is found, the 
incoming packet is wholly encapsulated in the GPRS 
Tunneling Protocol (GTP-GSM 09.60). The GTP PDU is 
transported via User Datagram Protocol (UDP) or 
30 Transport Control Protocol (TCP) 221 over Internet 

Protocol (IP) 223 to SGSN 205. SGSN 205 examines the 
GTP header and locates the corresponding MS-to-SGSN 
routing context. Based on the mobility management 



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PCT/US99/02429 



state of mobile station 201, SGSN 205 will preferably 
send the packet directly to mobile station 201 via the 
SNDCP/LLC functions when the location of mobile station 
201 is known to the cell-level. Alternately, SGSN 205 
will page mobile station 201 when the location of 
mobile station 201 is known only to the routing area 
level . 

In the alternate embodiment, the transmission of 
the encapsulated packet is delayed until mobile station 
201 responds with a paging response indicating the 
cell-level location of mobile station 201. The packet 
is then transferred across the Gb-interface 211 using 
the BSSGP 213 over Frame Relay to the RLC/MAC entity 
215, located in BSS 203, and subsequently across Urn 
air-interface 217 to mobile station 201. 

Mobile station 201 desiring to transmit data via 
the GPRS network places a service request to SGSN 205. 
SGSN 205 enables mobile station 201 to transmit data 
after authenticating mobile station 201 and activating 
the service request at GGSN 207. Prior to data 
transmission to mobile station 201, GGSN 207 activates 
a service request. GGSN 207 will initiate the paging 
of mobile station 201 if mobile station 201 is not 
currently communicating with an SGSN. GGSN 207 then 
sends a notification to SGSN 205, which activates a 
service request for mobile station 201. In this 
manner, SGSN 205, GGSN 207, and mobile station 201 all 
have the proper service request activation prior to 
data transmission. 

FIG. 3 depicts a protocol stack for local mobile 
station to a local wireline station communication. On 
receiving an attach request from mobile station 301 
that belongs to a pre-registered group of users, SGSN 



WO 99/50974 PCT/US99/02429 

-9- 

305 transfers to BSS 303 the contexts related to mobile 
station 301. In order to transfer the context, an 
additional signaling path between SGSN 305 and BSS 303 
must be established to communicate to SGSN 305 the 
5 required contexts associated with mobile station 301. 

A signaling pipe between BSS 303 and SGSN 3 05 is 
preferably configured by configuring a frame relay 
permanent virtual circuit. This approach does not 
involve any changes to standardized Gb interface 302. 
10 in an alternate embodiment, a signaling pipe between 

BSS 303 and SGSN 305 is configured using a bit in BSSGP 
protocol header 304 to indicate that the PDU is 
carrying signaling information. 

SGSN 305 may refresh the context of mobile station 
15 301 in BSS 303 when a parameter is changed due to 

mobile station- to-SGSN L3MM signaling. SGSN 305 
authorizes BSS 303 to process PDUs on its behalf. 
Similar procedures are invoked after every change or 
creation of a new context in the mobility management of 
20 mobile station 301 at SGSN 305. One such example is a 

change in the BSS serving the mobile station. The same 
signaling pipe is used to perform these functions. 

Two new additional messages have been introduced 
for the above purpose. The "Context Transfer" message 
25 from SGSN 305 to BSS 303 includes the required contexts 

that need to be transferred from SGSN 305 to BSS 303 
and directs BSS 303 to enable the BSS to route traffic 
to the corporate intranet for the context under 
consideration. The "Context Transfer ACK" message from 
30 BSS 303 to SGSN 305 informs SGSN 305 that the "Context 

Transfer" message has been received and appropriate BSS 
functions have been enabled. SGSN 305, on receiving 
the "Context Transfer ACK" message from BSS 303, 



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PCT/US99/02429 



chooses the appropriate transport plane for packets 
that either originate or are destined to mobile station 
301 or the PDP context under consideration. 

Similarly, additional signaling is introduced to 
delete a mobile station context at a first BSS after 
either a "GPRS Detach" or a change in the BSS serving 
the mobile station. After either or these situations, 
the context stored at the first BSS for the detached 
mobile station is deleted in the first BSS. To delete 
a PDP context stored at SGSN 305, SGSN 305 sends a 
"Purge Context" message to BSS 303. BSS 303, on 
deleting the appropriate PDP context, responds with a 
"Purge Context Ack" message. Similarly, a PDP context 
can be modified by SGSN 305 by sending a "Modify 
Context" message to BSS 303. BSS 303, on modifying the 
appropriate PDP context, responds with a "Modify 
Context Ack" message. This process is described in 
more detail in FIG. 7 below. 

In the preferred embodiment, BSS 303 processes 
only end-to-end user data, while all control PDUs are 
forwarded to SGSN 305 as before. Control PDUs relate 
to mobility management and other control information 
associated with a service request or a mobile station. 
BSSGP 309 passes all L3MM packets up to SGSN 305. A 
special bit is set to indicate that BSSGP 309 does not 
contain SNDCP/LLC frames and that the contents of BSSGP 
309 should be routed directly to the session handler in 
SGSN 305. This is similar to a situation where the 
contents of BSSGP 309 have been received from a local 
SNDCP layer. SGSN 305 forwards any Layer 3 PDUs 
received for mobile station 301 that has had the 
context of the mobile station has been downloaded to 
BSS 303, preferably using BSSGP 309. 



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PCT/US99/02429 



BSS 303 listens to all uplink RLC/MAC frames 
generated by the PCU and performs multiple functions. 
BSS 303 forwards Uplink PDUs from mobile stations for 
which no downloaded context exists in BSS 303 to SGSN 
305. BSS 303 also, upon receiving uplink PDUs from an 
MS that has had its context downloaded to BSS 303, 
recovers the complete layer 3 frame. Having extracted 
the LLC frame from the layer 3 frame, BSS 303 
determines the destination address of the packet. 

If BSS 303 has a downloaded context for the 
destination unit, the packet is headed to another 
mobile station being served by BSS 303. In this case, 
BSS 303 forwards the packet to the appropriate mobile 
station. In all other cases, the packet is forwarded 
to the corporate Intranet. The capabilities of the 
wireline network are relied upon to route data packets 
from the BSS to the appropriate host on the wireline 
network. The routing procedures route the packet to 
either the final destination in the corporate Intranet 
or to a Gateway which will then forward the packet to 
the appropriate gateway. 

The above procedure can be enhanced by allowing 
BSS 3 03 to route packets from a mobile station that 
belongs to the corporate Intranet to an appropriate 
GGSN 307, via SGSN 305, depending on the destination 
address or MS declared preferences. If a mobile 
station has more than one active service request, data 
from one service request can be forwarded to the 
corporate Intranet by BSS 303, while the other service 
requests have their data routed to SGSN 305. In this 
manner , mobile station 301 can access services located 
at the corporate intranet while still maintaining 
access to services provided via SGSN 305. 



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FIG. 9 depicts the contexts maintained by an SGSN 
for each associated mobile station. IMSI field 901 is 
the main reference -key. MM State field 951 represents 
the Mobility management state. The MM State 951 may be 
either IDLE, STANDBY, or READY. VLR Address field 952 
represents the SS7 address of the MSC/VLR currently 
serving this mobile station. New SGSN Address field 
953 is the IP address of the new SGSN where buffered 
and not sent N-PDUs should be forwarded to. TLLI field 
902 represents the Temporary Logical Link Identity. 
Routing Area field 954 is the current routing area. 
Cell Identity field 903 represents the current cell. 
Cell identity field 903 is preferably only valid when 
in the READY state. Authentication Triplets field 904 
represent authentication and ciphering parameters. Kc 
field 905 represents the currently used ciphering key. 
CKSN field 906 represents the ciphering key sequence 
number of Kc 905. Ciphering algorithm field 907 
represents the selected ciphering algorithm. MS Class 
908 represents the GPRS MS class. The GPRS MS classes 
are either A, B, or C. Classmark field 909 represents 
the MS classmark. DRX Parameters field 910 represents 
discontinuous reception parameters. Compression field 
911 represents negotiated data compression parameters. 
There are one set of parameters per QoS priority level. 
MNRF field 955 indicates whether activity from the 
mobile station should be reported to the HLR. Recovery 
field 956 indicates if the HLR or the VLR is performing 
database recovery. 

Each MM context can also include a PDP context 
900. PDP context 900 is a context associated with a 
particular PDP identifier. PDP context 900 includes 
the following fields. PDP Type field 912 represents 



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the PDP type, such as X.25 or IP. PDP Address field 
913 represents the PDP address, such as an X.121 
address. NSAPI field 914 represents the Network layer 
Service Access Point Identifier. NSAPI is also a PDP 
context index. PDP State field 915 represents the 
packet data protocol state. The packet data protocol 
states are INACTIVE or ACTIVE. GGSN Address field 916 
represents the DNS-type GSN name of the GGSN providing 
the Gi reference point for this PDP Address. GGSN 
Address in Use field 917 represents the IP address of 
the GGSN currently used by the activated PDP context. 
Dynamic Address Allowed field 957 specifies whether the 
mobile station is allowed to use a dynamic address. 
VPLMN Address Allowed field 958 specifies whether the 
mobile station is allowed to use a dynamic address 
allocated in the VPLMN. QoS Subscribed field 918 
represents the quality of service subscribed for this 
PDP context and includes four levels. 

The four levels refer to the four different 
Quality of Service (QoS) classes that provide different 
delay and other call characteristics. QoS Requested 
field 919 represents the quality of service requested 
upon PDP Context Activation and includes four levels. 
QoS Negotiated field 920 represents the quality of 
service negotiated for this PDP context and includes 
four levels. SND field 921 represents the GTP sequence 
number of the next downlink N-PDU to be sent to the 
mobile station, only for connection-oriented PDP types. 
SNU field 922 represents the GTP sequence number of the 
next uplink N-PDU to be sent to the GGSN, only for 
connection-oriented PDP types. Reordering Required 
field 923 specifies whether the SGSN shall reorder N- 
PDUs before delivering the N-PDUs to the MS. 



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Predetermined fields represented in FIG. 9 are 
also maintained at the BSS. These fields are 
explicitly communicated to the BSS by the SGSN. The 
fields in this predetermined set are IMSI field 901, 
TLLI field 902, Cell Identity field 903, Authentication 
Triplets field 904, Kc field 905, CKSN field 906, 
Ciphering algorithm field 907, MS Class 908, Classmark 
field 909, DRX Parameters field 910, Compression field 
911, PDP Type field 912, PDP Address field 913, NSAPI 
field 914, PDP State field 915, GGSN Address field 916, 
GGSN Address in Use field 917, QoS Subscribed field 
918, QoS Requested field 919, QoS Negotiated field 920, 
SND field 921, SNU field 922, and Reordering Required 
field 923. 

FIG. 4 depicts a local mobile station 401 to local 
wireline 401 communication. The preferred embodiment 
assumes that the second network is an IP-based network. 
LLC protocol 402 and SNDCP protocol 404 running at BSS 
403 use the filtered RLC/MAC PDUs 406 to recover the 
transmitted network layer protocol data units (PDUs) , 
such as IP packets. The network layer PDUs are then 
forwarded to the appropriate hosts on the wireline or 
wireless network. On receiving a context for mobile 
station 401 from the SGSN, BSS 403 generates a 
gratuitous Address Resolution Protocol (ARP) packet 
with its Layer 2 address 408 in the Layer 2 address 
field in the ARP packet. In IP networks, ARP packets 
refer to the packets generated by Address Resolution 
Protocol that is needed to create the mapping between 
Layer 3 (Network Layer) and Layer 2 (MAC) addresses. 
The ARP packet is a broadcast packet. The gratuitous 
ARP packet is transmitted only on the wireline network. 
Further, BSS 403 also responds to the ARP requests 



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directed towards mobile stations for which BSS 403 has 
a context. Therefore, any packets addressed to a 
mobile station that are currently associated with BSS 
403 are routed to BSS 403. Layer 3 frames destined for 
mobile station 401 are routed by default to the 
corporate gateway, unless BSS 403 advertises its 
ability to deliver packets to mobile station 401. 

In the situation when a mobile station moves out 
of the area served by a BSS, the contexts for that 
mobile station are removed at the BSS, preferably under 
the direction of the SGSN. The BSS then initiates 
procedures to ensure that data generated by users on 
the corporate intranet for the mobile station is routed 
to the corporate gateway. 

FIG. 5 depicts a flow chart for representing the 
routing of packets from a mobile host to a wireline 
host. A frame is received (501) from a mobile station. 
The BSS determines (503) whether the downloaded context 
for the mobile station is in the routing table. If the 
downloaded context is not in the routing table, the BSS 
forwards (505) the frame to the Packet Data Gateway. 
The process then ends (599) . The Packet Data Gateway 
forwards the frame to the appropriate packet data 
gateway. If the downloaded context for the mobile 
station is in the routing table, the BSS determines 
(507) if the destination address is local. If the 
address is not local, the BSS sends (509) the frame to 
the Packet Data Gateway. The process then ends (599) . 
If the destination address is local, the BSS determines 
(511) if the destination address is for a mobile 
station. If the frame is not for a mobile station, the 
BSS forwards (513) the frame to a second network. If 
the frame is for a mobile station, the BSS forwards 



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(515) the frame to the appropriate cell. The 
appropriate cell is the cell where the destination 
mobile station is currently affiliated. The process 

then ends (599) . 

FIG. 6 depicts a flow chart for representing the 
routing of packets from a wireline host to a mobile 
station. A frame is received (601), preferably by a 
BSS, from a fixed station. The BSS determines (603) 
whether the destination address is in the routing 
table. The routing table is a table located at the BSS 
that includes all the downloaded contexts. If the 
destination address is not in the routing table, the 
BSS discards (605) the frame. The process then ends 
(699) . If the destination address is in the routing 
table, the BSS fragments (607) the frame, if necessary. 
The BSS then appends (609) appropriate packet header 
and trailer information to the packet. The BSS then 
transmits (611) the packet on the wireless network. 
The process then ends (699) . 

FIG. 7 illustrates the call flow diagrams for 
various scenarios covered by the present invention. A 
decision (704) to download a context is made. The 
context preferably is associated with a mobile station 
701. In an alternate embodiment, the context is 
related to a mobile user of a mobile station. The 
Packet Data Gateway 703 downloads the context 705 to 
BSS 702. BSS 702 sends a context download ack 706 to 
indicate that the context has been successfully 
downloaded to BSS 702. 

In addition to downloading the context, the 
context can be deleted or modified. When a decision 
(707) is made to delete a context at BSS 702, a context 
purge message 708 is sent from Packet Data Gateway 703 



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to BSS 702. Upon deleting the context, BSS 702 send a 
context purge ack 709 to indicate that the context has 
been successfully deleted from BSS 702. 

When a decision (710) is made to modify a context, 
Packet Data Gateway 703 send a context modify message 
711 to BSS 702. Upon modifying the context, BSS 702 
send a context modify ack 712 to indicate to Packet 
Data Gateway 703 that the context has been successfully 
modified. 

The present invention provides Local Routing of 
Circuit Switched data for in-building applications by 
utilizing the GPRS access method for Local Routing of 
Circuit Switched data. The use of GPRS for access to 
Circuit Switched services enables the in-building 
system to offer mobile users access to circuit switched 
services. As a result, access to an InterWorking 
Function (IWF) at the MSC is not required. No MSG 
interaction is required for access to circuit switched 
services. 

The present invention provides a for routing a 
service request to access a circuit switched service to 
a packet data gateway in a communication system. The 
method comprises the steps of receiving a circuit 
switched service request at a Base Station System 
(BSS) . The circuit switched service request includes 
data. A context is transferred from a packet data 
gateway to the BSS. The data from the circuit switched 
service request is routed, based at least in part upon 
the context. 

Circuit Switched data services are provided by 
using data modems and fax modems attached to a Local 
Area Network (LAN) via a router, as depicted by 
communication system 800 in FIG. 8. Router 811, data 



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modems and fax modems 814 are off-the-shelf items that 
are commonly used today in corporate LAN modem pools. 
For additional user convenience, Fax Servers 814 can be 
LAN accessible so that mobile user 801 does not need to 
be connected when a fax is actually being sent to or 
received from PSTN 809. LAN accessible Circuit 
Switched facilities can be connected to the in-building 
PBX and to PSTN 809 for public network access. 

In an alternate embodiment of the present 
invention Local Routing for Public GPRS Networks, such 
as might be found in shopping malls or train stations, 
is provided. In this embodiment, mobile stations may 
not be required to be pre-registered at an SGSN in 
order for them to take advantage of Local Routing. In 
this embodiment, additional signaling occurs between 
the mobile station and the SGSN. The proposed 
signaling will enable the SGSN to advertise the 
possibility of local routing to access certain local 
resources to the MS. In addition, the mobile station 
can query the SGSN about the local routing capability 
and the services that can be accessed before its 
context is downloaded to a BSS. Further, the mobile 
station can indicate to the SGSN that it wishes to 
download its context to a BSS. 

Once it has been negotiated between the mobile 
station and the SGSN that the context associated with 
the mobile station should be downloaded to a BSS, the 
method previously described is invoked to complete the 
context download from the SGSN to the BSS. 

Returning to FIG. 8, in current communication 
systems, data packets between a GPRS mobile station 801 
and a wireline host traverse through a BSS 802 to a 
Serving GPRS Support Node (SGSN) 803. SGSN 803 



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typically forwards the data packets through GGSN 804. 
GGSN 804 will forward the data packets through another 
GGSN or an Internet Gateway 806. Corporate network 810 
then forwards the packet to an appropriate host. GGSN 
804 then routes the packets within an external network 
to a second GGSN (not shown) . The second GGSN is 
associated with a destination mobile station. In this 
embodiment, mobile station 801 is treated like a fixed 
network host. Consequently, no special handling is 
required to route packets between two mobile stations. 

The present invention provides local routing of 
data between mobile stations. In the preferred 
embodiment of the present invention, an in-building 
corporate Intranet 810 is connected directly to a pico- 
cellular GPRS BSS system 802 through LAN 817. Packets 
transmitted to and from wireline hosts in corporate 
Intranet 810 and wireless hosts are routed by serving 
BSS 802 without intervention from SGSN 803, except when 
the service request is first placed. Serving BSS 802 
is attached to corporate Intranet 810. Wireless hosts 
are treated as being a part of corporate Intranet 810. 
Similarly, data packets between two wireless hosts 
served by the same BSS could be switched by the BSS. 

To facilitate local routing, SGSN 803 transfers a 
context, or a portion thereof, associated with a 
service request to BSS 802. In the preferred 
embodiment, the step of transferring a context is 
initiated by mobile station 801 in communication with 
BSS 802. The step of transferring a context is 
initiated by mobile station 801 upon power up of mobile 
station 801. In an alternate embodiment, the step of 
transferring a context is initiated by the mobile 
station upon reselection of a cell, such as when 



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roaming. In this alternate embodiment, the method 
further comprising the step of deleting the context at 
the first BSS that the mobile station has just left. 

In an alternate embodiment, local routing of data 
between wireline stations and mobile station 801 is 
facilitated by mobile station 801 directing SGSN 803 to 
transfer the context associated with mobile station 801 
to BSS 802, 

The context can also be deleted at BSS 802. A 
context is transferred from a packet data gateway to 
BSS 802, such as when mobile station 801 powers up. 
Upon receiving an event, the context is deleted at BSS 
802. In a preferred embodiment, the event is the 
powering off of mobile station 801 that is in 
communication with BSS 802. Upon power off of mobile 
station 801, the context for mobile station 801 is 
deleted. In an alternate embodiment, the event is the 
expiration of an inactivity timer . The inactivity 
timer is set when a mobile user ceases activity. Upon 
the expiration of the timer, such as when the mobile 
station has not engaged in any communication activity 
for a predetermined period of time, the context for the 
mobile station is deleted at BSS 802. 

In a further alternate embodiment, the event is a 
message sent from the mobile station to the BSS for the 
context to be deleted at the BSS. This could occur 
when the mobile station wants to remain on-line but 
does not want to be contacted by other users. This 
embodiment provides flexibility and convenience to the 
mobile user. In addition, the mobile station and the 
packet data gateway can negotiate to determine who 
should inform the BSS when the context for the mobile 
station should be deleted at the BSS. 



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In the preferred embodiment. Local Routing of data 
between wireline stations 825 and mobile stations 801 
is facilitated by pre-registering a set of mobile 
stations belonging to corporate Intranet 810 with SGSN 
5 803. This is preferably accomplished through the 

allocation of specific IMSIs. 

The additional functionality of the present 
invention can be implemented in software using a 
standard hardware /software platform. Further, the 
10 present invention utilizes existing GPRS protocol 

stacks, thereby reducing the development effort. 

It should be understood that a mobile station 
refers to a physical mobile unit, such as a cellular 
telephone, that may be used by multiple and varied 
15 users. A mobile user refers to a user of a mobile 

station. A mobile user may utilize a mobile station by 
inserting an identification element, such as a smart 
card or the like, into the mobile station to identify 
the mobile user and provide access and privilege 
20 information, as well as information relating to billing 

accounts, place of work, and other elements which 
particularly identify the user and set forth the access 
privileges and capabilities of the mobile user while 
utilizing the mobile station. It should further be 
25 understood that the present invention works in relation 

to a mobile station, and also in relation to a mobile 
user. For instance, the context of a physical mobile 
station can be utilized to determine the routing of 
data coming to and from that particular mobile station. 
30 Alternately, the routing of data can be determined by 

utilizing the context of a mobile user. In this 
manner, a mobile user can physically use different 
mobile stations at different times, and still have the 



PCT/US99/02429 

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same access privileges across the varied mobile 
stations . 

The present invention of Local Routing of GPRS 
data provides many advantages over the prior art. The 

5 present invention provides a seamless extension of the 

wireline corporate Intranet to the wireless domain. In 
addition, the present invention provides reduced end- 
to-end delay since data between mobile stations and 
wireline hosts is optimally routed. Further the 

10 present invention provides reduced leased line costs 

since in-building traffic does not leave the premises. 
Still further, the present invention provides reduced 
traffic handling capacity required for the corporate 
wireline gateway and the SGSN, thereby ensuring 

15 increased system scalability. 

While this invention has been described in terms 
of certain examples thereof, it is not intended that it 
be limited to the above description, but rather only to 
the extent set forth in the claims that follow. 

20 



_,„„, v ,, PCT/US99/02429 
WO 99/50974 ^ 

Claims 



1. A method for routing data from a service request in 
a communication system, the method comprising the steps 
5 of: 

transferring a context from a packet data gateway 
to a Base Station System (BSS) coupled thereto; 

receiving a service request at the BSS, the 
service request including data; and 
10 routing, based at least in part upon the context, 

the data from the service request. 



2. A method for routing data from a service request in 
a communication system in accordance with claim 1, 
further comprising the step of deleting a context in a 
second BSS. 



> 0 3. A method for routing data from a service request in 

a communication system in accordance with claim 1, 
wherein the step of transferring a context from a 
packet data gateway comprises the step of transferring 
a context from a Serving GPRS Support Node. 

25 

4. A method for routing data from a service request in 
a communication system in accordance with claim 1, 
wherein the step of transferring a context is initiated 
30 by a mobile station in communication with the BSS. 



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5. A method for routing data from a service request in 
a communication system in accordance with claim 4, 
wherein the step of transferring a context is initiated 
by the mobile station upon power up of the mobile 
station. 

6 . A method for routing data from a service request in 
a communication system in accordance with claim 4, 
wherein the step of transferring a context is initiated 
by the mobile station upon reselection of a cell. 

7. A method for routing data from a service request in 
a communication system in accordance with claim 6, 
wherein upon reselection the mobile station is 
affiliated with a second BSS, the method further 
comprising the step of deleting a context in the BSS. 

8. A method for routing data from a service request in 
a communication system in accordance with claim 1, 
wherein the service request is transmitted by a mobile 
station, the method further comprising the step of 
transmitting a second service request from the mobile 
station. 

9. A method for routing data from a service request in 
a communication system, the method comprising the steps 
of: 

transferring a context from a packet data gateway 
to a Base Station System (BSS) coupled thereto; 



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receiving an event; and 

deleting, based upon the event, the context at the 
Base Station System. 



10. A method for routing data from a service request 
in a communication system, the service request being 
generated by a mobile station in communication with a 
BSS, the mobile station being associated with a mobile 
10 user, the method comprising the steps of: 

determining whether to include a context for the 
mobile user in the BSS; 

transferring, if it is determined to include the 
context in the BSS, the context from the packet data 
15 gateway to the BSS; 

receiving a service request at the BSS from a 
mobile station associated with the mobile user, the 
service request including data; and 

routing, if the context is located at the BSS, the 
20 data from the service request to a second network. 



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3/6 




SOFTWARE 
(EXISTING) 

EXISTING 
FUNCTIONALITY 



-405 



WIRELINE HOST 



FIG. 4 



FRAME RECEIVED FROM MS j-50' 




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FRAME RECEIVED FROM 
FIXED STATION 



4/6 
1-607 




FRAGMENT FRAME (IF NEEDED) \ ~607 

APPEND APPROPRIATE PACKET L 609 
HEADER /TRAILER INFORMATION I 

TRANSMIT PACKET ON 1-611 



WIRELESS NETWORK 




FIG. 6 



70L 



go 



r7Q 2 



| BSS | 

704-A DECISION TO DOWNLOAD CONTEXT MADE | 



703 



PACKET DATA | 
GATEWAY 



705 

MHTFXT DOWNLOAD S 



MHTFXT DOWNLOAD ACK 



706 



707^ DECISION TO DELETE CONTEXT MADE || 



708 

CONTEXT PURGE / 



CONTEXT PURGE ACK 



709 



710-1 DECISION TO MODIFY CONTEXT MADE || 



FIG. 7 



CONTEXT MODIFY 



CONTEXT MODIFY KK 



712 



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PCI7US99/02429 



5/6 




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PCT/US99/02429 



6/6 



901- 



952^ 



902^ 



903- 



905- 



907- 



909- 



911 



956- 



900 



("912-4 
914- 
916- 
957 
918 
920 



922 



MSI 



MM STATE 



VRL ADDRESS 



NEW SGSN ADDRESS 



TLLI 



ROUTING AREA 



CELL IDENTITY 



AUTHENTICATION TRIPLETS 



Kc 



CKSN 



CIPHERING ALGORITHM 



MS CLASS 



CLASSMARK 



DRX PARAMETERS 



COMPRESSION 



MNRF 



RECOVERY 



PDP TYPE 



POP ADDRESS 



NSAPI 



PDP STATE 



GGSN ADDRESS 



GGNS ADDRESS IN USE 



DYNAMIC ADDRESS ALLOWED 



VPLMN ADDRESS ALLOWED 



QoS SUBSCRIBED 



QoS REQUESTED 



QoS NEGOTIATED 



SND 



SNU 



REORDERING REQUIRED 



FIG. 9 



•951 



953 



954 



904 



906 



■908 



910 



955 



913 



915 



917 



■958 



919 



921 



■923 



INTERNATIONAL SEARCH REPORT 



International application No. 
PCT/US99/02429 



A. CLASSIFICATION OF SUBJECT MATTER 
IPC(6) : H04B 7/14 

, J1L (IPC) or U> boU, ^ cU^n ,PC 

a fi elds searched 

doouacation arched (ekoifietfioa •yoem followed by cU«if«tk» •ymboU) 



Minimum 
U.S. : 370/338.351-356>389,40l; 

i searched other than 



^ffr.tinn m th* extent that iuch documents are included in the fields searched 



j Electronic data base consulted during the international search (name 



of data base and, where practicable, search terms used) 



DOCUMENTS CONSIDERED TO BE RELEVANT 



Category* 



Citation of document, with indication, where appropriate, of the relevant passages 



US 5,504,804 A (WIDMARK et al.) 02 April 1996, abstract 



Relevant to claim No. 



1-10 



Q] Further documents are listed in the continuation of Box C. Q See patent family annex 



• 


Speeatl cM|ona of cited docum< 




•A' 


document defniina. the ganeral stat 
to be of particufcr itl«m« 


• of the en which b not considered 


•B* 


•artier document published on or 


eiWr tha ejtemeoonel filing data 




cued to eamblish the pubueation 
special reason <*» specified) 


O on priority clann(t) or which b 
data of another ciUUOD or other 


•O" 


document referring to an oral d 


iscloaurc. um, exhibition or other 


•p. 


document published prior to Iho is 


temeuonel filing data but bur than 



r _ „ after th* tntrrnaoooel filing da 

data and not « conflict with tha explication but cited t 



t of 

considered natal or 
when tha document a taken atone 



document of particular relevance; the claimed mv< 
considered to mvotva an inventive step when t 
combined wtth one or more other such documents, 1 
bang obvious to a person akilled in the an 

document member of the same patent family 



Date of the actual completion of the international search 
27 MARCH 1999 



Date of mailing of the international search report 

15JUN1999 



Name and mailing address of the ISA/US 
Commissioner of Patents and Trademarks 
Box PCT 

Washington, D.C 20231 
Facsimile No. (703) 305-3230 



Authorized officer 

JASPER KWOH WlS 1 ^ 
Telephone No. (703) 305-3900 



Hill 



Form PCT/1SA/210 (second sheet)(July 1992)* 



INTERNATIONAL SEARCH REPORT 



International application No. 
PCT/US99/02429 



A- CLASS1RCATION OF SUBJECT MATTER: 
USCL : 

370/338.351-356,389,401; 
455/510,511,517,524,525 



Form PCT/ISA/210 (extra shcct)(July 1992)*