U.S. patent application number 10/929236 was filed with the patent office on 2005-02-03 for system and method for packet data servicing node (pdsn) initial assignment and reselection.
Invention is credited to Basilier, Henrik, Chen, Ning Nicholas, Gustavsson, Roger, Julka, Vibhor.
Application Number | 20050025116 10/929236 |
Document ID | / |
Family ID | 24182171 |
Filed Date | 2005-02-03 |
United States Patent
Application |
20050025116 |
Kind Code |
A1 |
Chen, Ning Nicholas ; et
al. |
February 3, 2005 |
System and method for packet data servicing node (PDSN) initial
assignment and reselection
Abstract
An method for PDSN (Packet Data Serving Node) initial assignment
and re-selection in a wireless communication system is provided.
The method is implemented in PCF (Packet Control Function) within a
third-generation (3G) CDMA Radio Access Network (RAN). The
methodology reduces the number of point-to-point (PPP)
re-establishments, when a Mobile Station (MS) roams to a different
packet zone/PCF. The method generates a table of PDSN
identification numbers cross-referenced to the PDSN Internet
protocol (IP) addresses, residing with each PCF. A PDSN Id number
is selected from the table using the MS IMSI (International Mobile
Station Identifier) as a key to perform the selection. The present
invention methodology addresses the issue of forward and backward
compatibility, scalability, reliability, and load sharing in the
PDSN selection.
Inventors: |
Chen, Ning Nicholas; (San
Diego, CA) ; Basilier, Henrik; (Kensington, CA)
; Julka, Vibhor; (San Diego, CA) ; Gustavsson,
Roger; (San Diego, CA) |
Correspondence
Address: |
COATS & BENNETT, P.L.L.C.
P.O. Box 5
RALEIGH
NC
27602
US
|
Family ID: |
24182171 |
Appl. No.: |
10/929236 |
Filed: |
August 30, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10929236 |
Aug 30, 2004 |
|
|
|
09546823 |
Apr 11, 2000 |
|
|
|
Current U.S.
Class: |
370/349 ;
370/352 |
Current CPC
Class: |
H04L 61/10 20130101;
H04L 61/2092 20130101; H04L 67/1019 20130101; H04W 48/16 20130101;
H04L 29/12018 20130101; H04L 61/2015 20130101; H04L 29/06 20130101;
H04L 29/12311 20130101; H04L 61/2084 20130101; H04L 29/1232
20130101; H04W 8/26 20130101; H04L 67/1006 20130101; H04W 84/04
20130101 |
Class at
Publication: |
370/349 ;
370/352 |
International
Class: |
H04L 012/66; H04Q
007/00 |
Claims
1-27. Cancel
28. In a wireless communication system including one Packet Control
Function (PCF) and at least one Packet Data Serving Node (PDSN), a
method for determining which PDSN should be used for packet data
communications with a mobile station (MS), the method comprising:
maintaining a configuration table at the PCF being communicatively
coupled between the MS and at least one PDSN, said configuration
table having at least one unique PDSN identification (Id) number
listed therein, said at least one unique PDSN Id number being
respectively associated with the at least one PDSN; and selecting a
PDSN in response to a number of the PDSN Id numbers in the
configuration table.
29. The method of claim 28 further comprising: assigning a unique
MS Id number to the MS, wherein selecting the PDSN further includes
selecting in response to the MS Id number.
30. The method of claim 29, wherein assigning the unique MS Id
number includes using an International Mobile Station Identifier
(IMSI) of the MS for such assignment.
31. The method of claim 29, wherein the MS Id number is the
IMSI.
32. The method of claim 29, wherein the at least one PDSN comprises
n PDSNs, further wherein each of the n PDSNs has a unique Internet
protocol (IP) address, and further wherein the configuration table
has an ascending ordered sequence of the n PDSN Id numbers based on
the unique IP addresses of the n PDSNs.
33. The method of claim 32, wherein the selection of the PDSN
includes dividing the unique MS Id number by n.
34. The method of claim 33, wherein the selection of the PDSN
includes selecting the PDSN Id number equal to the remainder in the
quotient.
35. The method of claim 32, wherein the configuration table
includes one cross-reference between the at least one PDSN Id
number and a respective unique IP address associated with the PDSN
being communicatively coupled to the PCF.
36. The method of claim 35, wherein the configuration table
includes one cross-reference between the at least one PDSN Id
number and a dummy address associated with one of the n PDSNs that
is not communicatively coupled to the PCF.
37. The method of claim 36 further comprising reselecting an
alternative PDSN if the selection yields the PDSN Id number being
cross-referenced with the dummy address.
38. The method of claim 37, wherein the reselection of the
alternative PDSN includes selecting the alternative PDSN in
response to the PDSN Id number associated with the selected
PDSN.
39. The method of claim 37, wherein the reselection of the
alternative PDSN includes selecting the alternative PDSN in
response to the unique MS Id number.
40. The method of claim 29, wherein the at least one PDSN includes
n PDSNs, further wherein each of the n PDSNs has a unique Internet
protocol (IP) address, and further wherein the configuration table
has an ascending ordered sequence of some of the PDSN Id numbers
based on unique IP addresses of the PDSNs associated with said some
of the PDSN Id numbers.
41. The method of claim 40, wherein the configuration table
includes cross-references between the PDSN Id numbers and
respective unique IP addresses associated with the PDSNs being
communicatively coupled to the PCF.
42. The method of claim 41, wherein the configuration table
includes one cross-reference between one of the PDSN Id numbers and
a dummy address associated with one of the n PDSNs that is not
communicatively coupled to the PCF.
43. The method of claim 41 further comprising reselecting an
alternative PDSN if the selection yields the PDSN Id number being
cross-referenced with the dummy address.
44. The method of claim 32, wherein m of the n PDSNs are
communicatively coupled to the PCF, further the configuration table
includes cross-references between the IP addresses of the m PDSNs
and the respective PDSN Id numbers and cross-references between
dummy addresses and the respective (n-m) PDSN Id numbers, and
further wherein the PDSNs associated with the dummy addresses are
not communicatively coupled to the PCF.
45. A Packet Control Function (PCF) for selecting which one of n
Packet Data Serving Nodes (PDSNs) should be used for packet data
communications with a mobile station (MS), said PCF being
communicatively coupled between the MS and at least one PDSN and
being configured to: maintain a configuration table, said
configuration table having at least one unique PDSN identification
(Id) number listed therein, said at least one unique PDSN Id number
being respectively associated with the at least one PDSN; and
select a PDSN in response to a number of the PDSN Id numbers in the
configuration table.
46. The PCF of claim 45 further being configured to assign a unique
MS Id number to the MS, wherein the PCF selects the PDSN in
response to the MS Id number.
47. The PCF of claim 46, wherein the PCF uses an International
Mobile Station Identifier (IMSI) of the MS to assign the unique MS
Id number.
Description
BACKGROUND OF THE INVENTION
[0001] This invention generally concerns wireless communications
and, more particularly, a system and method for assigning a Packet
Data Serving Node (PDSN) to a wireless mobile station (MS), to
provide packet data services in a third-generation (3G) code
division multiple access (CDMA) communication system.
[0002] In the second generation CDMA systems specified by the
IS-95B standard, uplink data bursts from a MS to base station are
limited to a small number of frames, typically 8 or less. The data
rate is limited to 4.8 kbps, i.e., inferior to the one used by the
users active on the dedicated (voice) channels, which is 9.6 or
14.4 kilobits per second (kbps). The 3G CDMA, as described in
IS-2000 body of standards, is being designed to accommodate both
longer messages (more frames per message) and higher data rates to
support the communication packetized data. Data rates of 384 kbps
are envisioned. The ability of the 3G CDMA to communicate packet
data will permit users to seamlessly access the Internet with a
computer through a wireless telephone.
[0003] The transfer of large volumes of data between the MS and the
PDSN portal to the Internet will be aided by changing the 3G CDMA
system from the traditional PSTN circuit-switched system, where the
data network communication must be routed through the mobile
switching center (MSC), to a system where the PDSN can locally
connect to a radio access network (RAN) base station controller
(BSC) using frame relay, or some other link-layer transport capable
of carrying Internet protocol (IP) data packets. The linkage
between the wireless system and the Internet can be more
peer-to-peer and, therefore, simpler and faster, if the packet data
protocol can be maintained across the PDSN.
[0004] FIG. 1 illustrates the architecture for the 3G CDMA radio
access network (RAN), prior art. The packet control function (PCF)
and PDSN are two new entities defined by the third-generation
Partnership Project 2 (3GPP2) and are only relevant to packet data
calls. The cardinality of PDSN and PCF association is many-to-many,
meaning that it will be typical for many PCFs to be connected to
each PDSN. Likewise, it will be typical for many PDSNs to be
connected to each PCF.
[0005] When a packet data call is first established, by an MS
request for example, a BS and associated BSC are selected as
elements in the link. Typically, the BSC is associated with a
particular PCF, which may even be co-located at the BS. The PCF
must be connected to a PDSN, or a PDSN must be (initially) selected
for the MS. There is currently no IS-2000 standard for the initial
PDSN assignment.
[0006] Furthermore, the packet data link between the MS and PDSN,
once initially selected, may become dormant as the MS ceases to
communicate packet data. In this situation the air interface
traffic and control channels are released, but the point-to-point
(PPP) connection between the PDSN and the MS are maintained. It is
foreseeable that a dormant MS will roam. Regardless of the
relationship between PCFs and BCSs, a dormant MS will roam to a
different packet zone (i.e. a new PCF). The new PCF must be
notified and it must then establish a new connection to one of the
PDSNs. It is highly desirable that the new PCF selects the PDSN
that was previously selected by the old PCF. In this manner, the
overhead required to re-establish a PPP connection can be
minimized, even as dormant handoff occurs between the old and new
PCFs, where the previous PDSN already has the PPP connection.
[0007] The current 3G CDMA network architecture does not have an
interface or a mechanism defined to inform the new PCF of the PDSN
which was previously selected by the old PCF, nor is there a third
entity that overlooks all resources in the entire network.
[0008] In would be advantageous if there was a way for the same
PDSN to be selected for packet data communications to a MS in the
dormant state, in the event that a new PCF must be selected.
[0009] It would be advantageous if the same PDSN could be selected
in a MS dormant state reselection process using the existing
network architecture.
[0010] It would be advantageous if the same PDSN could be selected
in a MS dormant state reselection process without the PCF and PDSN
units having special knowledge of each other, without special
network communications, or without the use of an independent
network entity to control dormant state reselections.
SUMMARY OF THE INVENTION
[0011] A method is provided for selecting a PDSN for packet data
communications with a MS in a wireless communication system. The
method comprises: generating a record of unique PDSN
(identification) numbers; and selecting a PDSN identification (Id)
number in response to the number of PDSN Id numbers in the record.
The selection of the PDSN is also responsive to the MS
International Mobile Station Identifier (IMSI).
[0012] In one aspect of the invention, the wireless communication
system includes a plurality of m PCFs and a plurality of n PDSNs
with unique IP addresses. Then, the method comprising: at each PCF,
generating a record of PDSN Id numbers; and selecting the PDSN Id
number in response to the total number (n) of PDSN Id numbers in
the record, and in response to the MS IMSI.
[0013] The record of PDSN Id numbers is a table with an ordered
sequence of the PDSN Id numbers cross-referenced to the PDSN IP
addresses. The selection of the first PDSN Id number includes
dividing the first MS IMSI by the number of (n) PDSNs in the table.
Specifically, the selection of the first PDSN Id number includes
selecting the PDSN with the number equal to the remainder in the
quotient, when the first MS IMSI divided by n.
[0014] Not all the PDSNs listed in the selection table need be
connected to the first PCF hosting the table. When the first PCF is
not connected to the IP address associated with the first PDSN Id
number, the connection cannot be made. Then, the method further
comprises reselecting an alternate PDSN Id number, after the first
PDSN Id number has been calculated. In one aspect of the invention,
the reselection of an alternate PDSN Id number includes varying the
first PDSN Id number, typically by adding "1", and dividing that
varied number by n. Then, the PDSN with the number equal to the
remainder in the quotient is selected.
[0015] Alternately, the reselection of an alternate PDSN Id number
includes: removing the first PDSN Id number and associated IP
address from the table; dividing the MS IMSI by the number of PDSNs
remaining in the table; and selecting the PDSN Id number equal to
the remainder in the quotient.
[0016] A wireless communication system for communicating packet
data is also provided. The system comprises a first mobile station
(MS) having a unique identification number (Id), such as its IMSI,
and a transceiver for wireless packet data communications. The
system comprises a plurality of m PCFs. Each PCF has a port for
packet data communications with MSs, and with at least one of a
plurality of n PDSNs. Each PDSN has a port for packet data
communications, a unique IP address, and a unique (identification)
number. Each PCF includes a table with an ordered sequence of the n
PDSN Id numbers cross-referenced with the n IP addresses. Because
of the common ordering of PDSN Id numbers in the tables, each PCF
selects the same PDSN Id number for packet data communications
involving the first MS. The selection process is responsive to the
first MS Id, and the number of PDSNs in the table.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 illustrates the architecture for the 3G CDMA Radio
Access Network (RAN), prior art.
[0018] FIG. 2 depicts an exemplary connection of PCF units and PDSN
units in a wireless communication system.
[0019] FIGS. 3 and 4 depict exemplary partially-connected network
of PCF and PDSN units.
[0020] FIG. 5 depicts the addition of a PDSN unit to a network of
PCF clusters.
[0021] FIG. 6 is a flowchart illustrating the present invention
method for selecting a PDSN for packet data communications with a
first MS.
[0022] FIG. 7 is a flowchart illustrating an alternate depiction of
the present invention method for selecting a PDSN for packet data
communications with a first MS.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0023] In short, the heart of the invention is a methodology
embodied in a set of machine executable instructions. Typically,
the instructions are written in a medium which can be accessed as
memory by a computer, or which can be read by a computer. The set
of instructions are typically embodied as a computer application
which orders the computer microprocessor to perform the series of
steps needed to cause a PCF to select a PDSN in accordance with the
algorithm described in detail below.
[0024] A PDSN table must be configured at PCF. Each PCF maintains a
table that includes all PDSNs it is connected to. Each table entry
must contain (but is not limited to) a PDSN identification (Id)
number, and an IP Address associated with the PDSN. It is important
that the PDSN Id numbers are assigned consistently, stored in a
predetermined ordered sequence (ascending or descending) in all
PCFs. An example of such a table, such as might be configured in a
PCF is shown below (Table 1).
1 TABLE 1 PDSN Number IP Address 0 aaaa 1 bbbb . . . n - 1 xxxx
[0025] The PDSNs are (locally) numbered from 0 to (n-1) and are
stored in ascending order based on PDSN IP addresses. It is assumed
that aaaa<bbbb< . . . <xxxx, and that n is the total
number of PDSNs available to this PCF. As explained in more detail
below, a PDSN can be entered into a selection table, even if that
PDSN is not connected to the PCF hosting the table.
[0026] The PCF determines which PDSN to select for a particular MS
based on the unique identification number (Id) of the MS.
Typically, the IMSI is used. Then, the following calculation is
performed:
PDSNNo.=(Mobile IMSI) modulo n
[0027] It is understood that modulo n is a computational process
where the remainder of a quotient is used as the answer. In this
case the quotient is the MS IMSI divided by n. Note that n is the
total number of locally available PDSNs to this PCF, not that of
the entire network. However, when the network is fully connected,
as explained below, the "local" n becomes the total number of PDSNs
in the entire network.
[0028] FIG. 2 depicts an exemplary connection of PCF units and PDSN
units in a wireless communication system 10. There are n PDSN units
with the PDSN Id Nos. of "0" (12), "1" (14), and "2" (16), where n
is equal to three. The respective IP addresses of PDSN units 12-16
are "001", "002", and "003", shown in Table 2 corresponding to an
ordered sequence of PDSN Id numbers. Also shown in FIG. 2 are m PCF
units, PCF 1 (18), PCF 2 (20), and PCF 3 (22), where m is equal to
three. The PCF units 10-22 are all configured with a PDSN initial
selection table. Table 2 is the PDSN selection table for PCF 1
(18). Both the PCF and PDSN units have ports for the communication
of packet data. A first MS 24 is shown having a transceiver for the
communication of packet data. The first MS 24 is connected to the
first PCF 18 through other elements in the system 10, not shown.
PCF 1 (18) is shown assigned to interface the first MS 24 with a
PDSN.
2 TABLE 2 PDSN Number IP Address 0 001 1 002 2 003
[0029] Assuming that the first MS 24 has an IMSI of 3,000,001, then
the division of 3,000,001 by n (3) yields a remainder of "1". PDSN
1 (14) is chosen having the IP address of "002".
[0030] If the selected PDSN is not available, for reasons such as
lost of connection, exceeding PDSN capacity, or simply no existing
physical link, the PCF re-selects an alternative PDSN from the
table, based on Mobile Station IMSI. This continuous selection
process may iterate for a maximum of (n-1) times, until a PDSN is
finally selected.
[0031] In one aspect of the invention, the continuous selection
calculates a reselected PDSN as follows:
PDSN No.=(last selected PDSN No.+1) modulo n
[0032] In terms of the example given above where n=3 and the IMSI
is 3,000,001:
PDSN No.=(1+1) modulo 3=2
[0033] Now PDSN 2 (16) is chosen having the address of "003". One
problem with this reselection method is that there is a statistical
tendency for MSs to reselect a common PDSN, causing a load
imbalance in the system.
[0034] In another aspect of the invention the reselection process
is handled differently. The number n is reduced by one, and the
calculation repeated as follows:
PDSN No.=(Mobile IMSI) modulo (n-1)
[0035] However, this process does not always work. In terms of the
example given above where n=3 and the IMSI is 3,000,001:
PDSN No.=(3,000,001) modulo 2=1,
[0036] which is the same result received in the initial selection
where PDSN 1 (14) was selected. That is, the reselection process
failed to select a new PDSN. However, this concept can be made to
work with modifications. One modification involves temporarily
removing the last selected PDSN Id No. from the table, and
renumbering the table.
[0037] For example, assuming that the initial selection process
selects PDSN 1 (14) (i.e. PDSN No.=IMSI % 3=1), but PDSN 1 (14) is
not available. Then, the PDSN table is temporarily changed, for
this mobile 24 only, to Table 3. Alternately stated, Table 3 is the
PDSN selection table of PCF 1 (18), modified for the reselection
process, when the initially selected PDSN is not available.
3 TABLE 3 PDSN No. IP Address 0 001 1 003
[0038] The old PDSN 1 (14) is temporarily removed from the table,
and the old PDSN 2 (16) now becomes PDSN 1, as a result of keeping
the PDSN Id numbers in an ordered sequence, or ascending
re-ordering. The continuous selection uses the updated table to
select between PDSN of address "001" and "003" using IMSI %
(modulo) 2 in this example. After a successful continuous
selection, the original PDSN table (with three entries in this
example, Table 2) is restored for next normal Selection as
described above.
[0039] FIGS. 3 and 4 depict exemplary partially-connected network
of PCF and PDSN units. To increase the likelihood of re-selecting
the same PDSN in a partially connected network, more rows can be
inserted in the PDSN table (through network management), so that
all PDSNs in a cluster are uniquely numbered, and the neighboring
PCFs use the same table. Table 4, below, depicts the PDSN selection
tables configured in PCF 1 (18) and PCF 2 (20) of FIG. 3.
4TABLE 4 @PCF1: @PCF2: PDSN No. IP Address PDSN No. IP Address
Before Adjustment: (assume IP address a < b < c < d and
ascending ordering used) 0 001 0 002 1 002 1 003 2 003 2 004 0 001
0 "dummy" address flag no connection After Adjustment 1 002 1 002 2
003 2 003 3 . . . "dummy" address flag no 3 004 connection
[0040] With respect to FIG. 3 and Table 4, PCF 1 (18) is shown
connected to PDSN 0 (12), PDSN 1 (14), and PDSN 2 (16). PCF 2 (20)
is shown connected to PDSN 2 (16) and PDSN 3 (26). If the first MS
24 enters the dormant mode, and is reassigned to PCF 2 (20) as a
result of roaming, it would be desirable if PCF 2 (20) selects the
same IP address that PCF 1 (18) was using for packet data
communications. In a fully connected system, the selection process
can be forced to yield the same IP address for the first MS 24,
regardless of which PCF is assigned to the first MS 24. In a system
that is not fully connected the same result is guaranteed if the
selected PDSN happens to be connected to every PCF.
[0041] Assuming that the first MS IMSI is still 3,000,001, and n is
equal to 4, the first PCF 18 selects PDSN 1 (14) as follows:
PDSN Id No.=(3,000,001) modulo 4=1
[0042] If the first MS 24 is later assigned to the second PCF 20,
the selection process selects the same PDSN Id number, because the
PCFs use the same sequence in their tables. Because the first PCF
18 and the second PCF 20 are both connected to PDSN 1 (14) the IP
address is maintained without the requirement of a new PPP being
established.
[0043] Table 5, below, depicts the PDSN selection tables configured
in PCF 1 (18) and PCF 2 (20) of FIG. 4.
5TABLE 5 @PCF1: @PCF2: PDSN No. IP Address PDSN No. IP Address
Before Adjustment: (assume IP address a < b < c < d and
ascending ordering used) 0 001 0 003 1 002 1 004 2 003 0 001 0
"dummy" address flag no connection After Adjustment 1 002 1 "dummy"
address flag no connection 2 003 2 003 3 . . . "dummy" address flag
no 3 004 connection
[0044] FIG. 4 and Table 5 illustrate a situation similar to the
example of FIG. 3 (Table 4), except that the second PCF 20 is not
connected to PDSN 1. When the first MS 24 is assigned to the second
PCF 20, the table will select PDSN 1 (14) just as the first PCF 18
did. This is because the tables have the same ordered sequence of
PDSN Id numbers. However, because the second PCF 20 is not
connected to PDSN 1 (14), a different PDSN must be selected. The
reselection process that follows has been described in detail
above.
[0045] The invention advantageously ensures that the first mobile's
PPP connection is maintained for the duration of a packet call as
best as possible. The likelihood of selecting the same PDSN when a
MS roams to a new PCF is a function of the actual PCF-PDSN
connectivity at the new and old PCF. Although the selection process
does not guarantee consistent PDSN selections if the network is
deployed such that PDSNs and PCFs are not fully connected, the
probability of selecting the same PDSN increases as the
connectivity increases. In the degenerate case (full connectivity),
this selection algorithm always selects the same PDSN for a given
MS Id, because every PCF has the same PDSN table and uses the same
n (the "global" n) for modulo operation.
[0046] The unique selection process described herein is backward
and forward compatible. The selection method can be implemented
without a need for signaling or architecture changes to the
existing 3G CDMA network architecture, so that it is backward
compatible. The selection process affects only a single network
component, the PCF. The software required to support enhancements
and changes to future all-IP architecture is easily modified, so
the PDSN selection is forward compatible.
[0047] FIG. 5 depicts the addition of a PDSN unit to a network of
PCF clusters. The selection method also addresses scalability,
because the n used for modulo operation is the number of PDSNs
locally available to the PCF. When removing a PDSN and the
associated physical link, "dummy" entries can be used to replace
the removed PDSN so that other entries in a PDSN table are not
changed. PDSN selections will therefore not be disturbed. When
adding a PDSN, only the (local) PCFs that need to add or remove a
PCF-PDSN physical link need to be updated, not the entire network.
Therefore, only the locally affected PCFs may suffer from
re-selecting a different PDSN in this case (and if MS roams).
[0048] Expanding cluster 2, where a new PDSN (PDSN 4) is being
added, will not affect cluster 1. Only those PCFs that will add a
direct link with the new PDSN are effected, such as PCF 2.
Therefore, all MSs that roam within cluster 1 will not be
affected.
[0049] FIG. 6 is a flowchart illustrating the present invention
method for selecting a PDSN for packet data communications with a
first MS. Step 100 includes a wireless communication system with at
least one Packet Control Function (PCF) and at least one Packet
Data Servicing Node (PDSN). Although the method describes a
sequence of numbered steps for clarity, no order should be inferred
from the numbering unless explicitly stated. Step 102 generates a
record of unique PDSN Id numbers. Step 104 assigns a unique MS
identification number (Id) to the first MS. Step 106 is a product
where a PDSN is selected in response to the number of PDSN Id
numbers in the record. The selection of the PDSN in Step 106 also
includes the selection of the PDSN being responsive to the first MS
Id.
[0050] In some aspects of the invention the system in Step 100
includes n PDSNs, with each PDSN in the system having a unique
Internet protocol (IP) address. Then, the generation of the record
of PDSN addresses in Step 102 includes creating a table with an
ordered sequence of the PDSN Id numbers cross-referenced to the IP
addresses. The selection of the PDSN in Step 106 includes dividing
the first MS Id by the number of (n) PDSNs. More specifically, the
selection of the PDSN in Step 106 includes selecting the PDSN Id
number equal to the remainder in the quotient, when the first MS Id
divided by n.
[0051] In some aspects of the invention the method further
comprises Step 101, where the first MS communicates with a first
PCF to request packet data communications. The generation of the
table of PDSN addresses in Step 102 includes the first PCF having a
table of cross-referenced PDSN Id numbers and IP addresses. The
selection of the PDSN Id number in Step 106 includes using the
table of the first PCF to calculate the PDSN Id number.
[0052] FIG. 7 is a flowchart illustrating an alternate depiction of
the present invention method for selecting a PDSN for packet data
communications with a first MS. Step 200 includes a wireless
communication system with a plurality of m Packet Control Functions
(PCFs) and a plurality of n Packet Data Servicing Node (PDSNs)
having unique Internet protocol (IP) addresses. Step 202, at each
PCF, generates a record of PDSN Id numbers. Step 204 assigns a
unique MS identification number (Id) to the first MS. Typically,
the IMSI number is used. Step 206 is a product where a first PDSN
Id number is selected in response to the total number (n) of PDSN
Id numbers in the record. The selection of the first PDSN Id number
in Step 206 also includes selecting the first PDSN Id number in
response to the first MS Id.
[0053] In some aspects of the invention Step 201 assigns a first
PCF, to establish packet data communications between the first MS
and a PDSN. Then, the selection of the first PDSN Id number in Step
206 includes the first PDSN Id number being selected, regardless of
which PCF is assigned. Step 208 routes packet data communications
between the first MS and the IP address corresponding to the
selected PDSN Id number, through the assigned PCF.
[0054] The generation of the record of PDSN Id numbers in Step 202
includes creating a table with an ordered sequence of the PDSN Id
numbers cross-referenced to the IP addresses. Then, the selection
of the first PDSN Id number in Step 206 includes dividing the first
MS Id by the number of (n) PDSNs in the table. Further, the
selection of the first PDSN Id number in Step 206 includes
selecting the PDSN Id number equal to the remainder in the
quotient, when the first MS Id divided by n.
[0055] In some aspects of the invention, the system of PDSNs and
PCFs are not fully connected, which complicates the PDSN selection
process. That is, Step 200 includes the first PCF being connected
to a IP address corresponding to the second PDSN Id number, but not
to the IP address corresponding the first PDSN identification
number. Then, Step 207 reselects an alternate PDSN Id number, after
the first PDSN Id number has been calculated.
[0056] In some aspects of the invention, the reselection of an
alternate PDSN Id number in Step 207 includes varying the first
PDSN Id number, dividing that varied first PDSN Id number by n, and
selecting the PDSN Id number equal to the remainder in the
quotient. The first PDSN Id number can be randomly varied for the
reselection of an alternate PDSN Id number, or varied by adding a
"1".
[0057] Alternately, the reselection of an alternate PDSN Id number
in Step 207 includes: removing the first PDSN Id number and
associated IP address from the table; dividing the first MS Id by
the number of PDSNs remaining in the table; and selecting the PDSN
Id number equal to the remainder in the quotient.
[0058] With respect to load balancing, the present invention
selection method causes the load of services to be evenly
partitioned among locally available PDSNs on the basis of the MS
IMSI. When approaching PDSN-PCF full connectivity, the load is
evenly distributed in the entire network. The present invention
uses a simple and reliable algorithm. It is easy to administer,
impacts only a single network entity, the PCF, and it requires few
resources, just memory and computing power. Although specific
examples have been presented to clarify the concept of the
invention, the present invention is not limited to the particular
embodiments mentioned above. Other variations and embodiments will
occur to those skilled in the art.
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