U.S. patent application number 10/807636 was filed with the patent office on 2004-09-09 for method and apparatus for efficient paging and registration in a wireless communications network.
Invention is credited to Chen, An Mei, Rosen, Eric C..
Application Number | 20040176113 10/807636 |
Document ID | / |
Family ID | 32324405 |
Filed Date | 2004-09-09 |
United States Patent
Application |
20040176113 |
Kind Code |
A1 |
Chen, An Mei ; et
al. |
September 9, 2004 |
Method and apparatus for efficient paging and registration in a
wireless communications network
Abstract
Method and apparatus for optimizing registration and paging in a
group communication system use mobility of the mobile stations to
minimize the frequency of registrations performed by the mobile
stations as well as the area of paging the mobile stations. When
the mobile stations have a low mobility status, the base station
reduces the area of paging the mobile stations so that the paging
channel load is reduced.
Inventors: |
Chen, An Mei; (San Diego,
CA) ; Rosen, Eric C.; (Solana Beach, CA) |
Correspondence
Address: |
Qualcomm Incorporated
Patents Department
5775 Morehouse Drive
San Diego
CA
92121-1714
US
|
Family ID: |
32324405 |
Appl. No.: |
10/807636 |
Filed: |
March 23, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10807636 |
Mar 23, 2004 |
|
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|
10300490 |
Nov 19, 2002 |
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Current U.S.
Class: |
455/458 ;
455/435.1; 455/445; 455/567 |
Current CPC
Class: |
H04W 4/06 20130101; H04W
60/04 20130101; H04W 68/02 20130101; H04W 48/20 20130101; H04W
68/04 20130101 |
Class at
Publication: |
455/458 ;
455/567; 455/445; 455/435.1 |
International
Class: |
H04Q 007/20 |
Claims
What is claimed is:
1. A method for paging a target mobile station (MS), the method
comprising: receiving information destined for a target MS; and
paging the target MS at a paging area that is centered at a cell,
in which the target MS last registered, and expands by a predefined
number of cells around the cell.
2. The method of claim 1, further including sending the information
to the target MS, if the target MS is located.
3. The method of claim 2, further including determining a
neighboring base station controller (BSC) that can locate the
target MS, if the target MS is not located.
4. The method of claim 3, further including sending the information
to the neighboring BSC that locates the target MS for delivery to
the target MS.
5. The method of claim 3, further including determining whether a
mobile station controller (MSC) can locate the target MS, if no BSC
connected to the MSC could locate the target MS.
6. The method of claim 5, further including sending the information
to the MSC for delivery to the target MS, if the MSC locates the
target MS.
7. A computer-readable medium storing codes for enabling a
processor to perform a method for paging a target mobile station
(MS), the method comprising: receiving information destined for a
target MS; and paging the target MS at a paging area that is
centered at a cell, in which the target MS last registered, and
expands by a predefined number of cells around the cell.
8. The computer-readable medium of claim 7, the method further
including sending the information to the target MS, if the target
MS is located.
9. The computer-readable medium of claim 8, the method further
including determining a neighboring base station controller (BSC)
that can locate the target MS, if the target MS is not located.
10. The computer-readable medium of claim 9, the method further
including sending the information to the neighboring BSC that
locates the target MS for delivery to the target MS.
11. The computer-readable medium of claim 9, the method further
including determining whether a mobile station controller (MSC) can
locate the target MS, if no BSC connected to the MSC could locate
the target MS.
12. The computer-readable medium of claim 11, the method further
including sending the information to the MSC for delivery to the
target MS, if the MSC locates the target MS.
13. An apparatus for paging a target mobile station (MS),
comprising: means for receiving information destined for a target
MS; and means for paging the target MS at a paging area that is
centered at a cell, in which the target MS last registered, and
expands by a predefined number of cells around the cell.
14. The apparatus of claim 13, further including means for sending
the information to the target MS, if the target MS is located.
15. The apparatus of claim 14, further including means for
determining a neighboring base station controller (BSC) that can
locate the target MS, if the target MS is not located.
16. The apparatus of claim 15, further including means for sending
the information to the neighboring BSC that locates the target MS
for delivery to the target MS.
17. The apparatus of claim 15, further including means for
determining whether a mobile station controller (MSC) can locate
the target MS, if no BSC connected to the MSC could locate the
target MS.
18. The apparatus of claim 17, further including means for sending
the information to the MSC for delivery to the target MS, if the
MSC locates the target MS.
19. A base station controller (BSC) for paging a target mobile
station (MS), comprising: a receiver capable of receiving
information from a target MS; a transmitter capable of transmitting
information to the target MS; and a processor capable of carrying
out a method for paging the target MS, comprising: receiving
information destined for a target MS; and paging the target MS at a
paging area that is centered at a cell, in which the target MS last
registered, and expands by a predefined number of cells around the
cell.
20. The base station controller of claim 19, the method further
including sending the information to the BSC for delivery to the
target MS, if the BSC locates the target MS.
21. The base station controller of claim 20, the method further
including determining a neighboring BSC that can locate the target
MS, if the BSC could not locate the target MS.
22. The base station controller of claim 21, the method further
including sending the information to the neighboring BSC that
locates the target MS for delivery to the target MS.
23. The base station controller of claim 21, the method further
including determining whether a mobile station controller (MSC) can
locate the target MS, if no BSC connected to the MSC could locate
the target MS.
24. The base station controller of claim 23, the method further
including sending the information to the MSC for delivery to the
target MS, if the MSC locates the target MS.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present Application for Patent is a divisional and
claims priority to patent application Ser. No. 10/300,490 entitled
"Method and Apparatus for Efficient Paging and Registration in a
Wireless Communications Network" filed Nov. 19, 2002, pending, and
assigned to the assignee hereof and hereby expressly incorporated
by reference herein.
FIELD
[0002] The present invention relates to point to multi-point
communications systems. More specifically, the present invention
relates to methods and apparatus for optimizing the frequency of
registrations as well as the area of paging in a wireless group
communication network.
BACKGROUND
[0003] In wireless communications systems, registration is the
process by which the mobile station notifies the base station of
its location, status, identification, slot cycle, and other
characteristics. The mobile station informs the base station of its
location and status so that the base station can efficiently page
the mobile station when establishing a mobile station-terminated
call. On the other hand, paging a mobile station includes the act
of seeking the mobile station when a call is to be placed to that
mobile station. To conserve system capacity, reduce service cost,
and save battery life, it is desirable to minimize registration as
well as paging channel load. However, the act of minimizing
registration may be accompanied by a considerable increase in the
paging area, and hence an increase in the paging channel load.
Current registration and paging techniques are not optimized based
on the mobility of the mobile stations.
[0004] For example, a class of wireless services intended for
quick, efficient, one-to-one or one-to-many (group) communication
has existed in various forms for many years. In general, these
services have been half-duplex, where a user presses a
"push-to-talk" (PTT) button on a phone/radio to initiate a group
call. If granted the floor, the talker then generally speaks for a
few seconds. After the talker releases the PTT button, other users
may request the floor. These services have traditionally been used
in applications where one person, a "dispatcher," needs to
communicate with a group of people, such as field service personnel
or taxi drivers, which is where the "dispatch" name for the service
comes from. Similar services have been offered on the Internet and
are generally known as "voice chat." A key feature of these
services is that mobile stations participating in a group call
generally tend to be of low mobility. Therefore, registration and
paging may be optimized accordingly.
[0005] There is a need, therefore, for mechanisms to minimize
registration without having to page in a wider area. There is also
a need to optimize registration and paging of a group of mobile
stations based on the mobility of the mobile stations.
SUMMARY
[0006] The disclosed embodiments provide novel and improved methods
and apparatus for optimizing registration and paging of mobile
stations in a wireless communication network. In one aspect, a
method in a mobile station (MS) for registering the MS with a base
station (BS) includes the steps of determining the number of cells
identified in a first list and registering the MS with the BS, if
the number of cells identified in the first list is equal to a
predetermined limit.
[0007] In one aspect, a method for paging a target mobile station
(MS) includes the steps of receiving information destined for a
target MS and paging the target MS at a paging area that is
centered at a cell, in which the target MS last registered, and
expands by a predefined number of cells around the cell.
[0008] In another aspect, an apparatus for paging a target mobile
station (MS) includes a memory unit, a receiver, a transmitter, and
a processor communicatively coupled with the memory unit, the
receiver, and the transmitter. The processor is capable of
executing instructions to carry out the above-mentioned
methods.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The features and advantages of the present invention will
become more apparent from the detailed description of the
embodiments in connection with the drawings set forth below:
[0010] FIG. 1 illustrates a group communications system;
[0011] FIG. 2 illustrates an embodiment for a base station and a
mobile station operating in FIG. 1;
[0012] FIG. 3 illustrates how several mobile stations interact with
a group call server;
[0013] FIG. 4 illustrates an embodiment for a group call server in
FIG. 1;
[0014] FIG. 5 illustrates a call-setup process;
[0015] FIG. 6 illustrates call-signaling details for a
network-initiated information delivery process;
[0016] FIG. 7 illustrates a process for buffering location
information for mobile stations;
[0017] FIG. 8 illustrates a configuration for a group communication
network;
[0018] FIG. 9 illustrates an alternative configuration for a group
communication network;
[0019] FIG. 10 illustrates a network-initiated information delivery
process;
[0020] FIG. 11 illustrates a registration process;
[0021] FIG. 12 illustrates a cell layout; and
[0022] FIG. 13 illustrates a paging process.
DETAILED DESCRIPTION
[0023] Before several embodiments are explained in detail, it is to
be understood that the scope of the invention should not be limited
to the details of the construction and the arrangement of the
components set forth in the following description or illustrated in
the drawings. Also, it is to be understood that the phraseology and
terminology used herein is for the purpose of description and
should not be regarded as limiting.
[0024] FIG. 1 illustrates a functional block diagram of a group
communication system 100, for implementing one embodiment. Group
communication system 100 is also known as a push-to-talk (PTT)
system, a net broadcast service (NBS), a dispatch system, or a
point-to-multi-point communication system. In one embodiment, group
communication system 100 includes a group call server 102, which
may be deployed in either a centralized deployment or a
regionalized deployment.
[0025] Group mobile stations (MSs) 104 and 106, which may be
deployed such as cdma2000 handset, for example, may request packet
data sessions using a data service option. Each MS may use the
session to register its Internet Protocol (IP) address with the
group call server 102 to perform group call initiations. In one
embodiment, group call server 102 is connected to the service
provider's packet data service nodes (PDSNs) 114 through service
provider's network 116. Mobile stations 104 and 106, upon
requesting packet data sessions from the wireless infrastructure,
may have IP connectivity to group call server 102 through the PDSNs
114. Each PDSN may interface to a base station controller (BSC)
through a packet control function (PCF) 108 and a network 112. The
PCF may be co-located with the BSC within a base station (BS) 110.
A number of BSCs may be connected to a mobile station controller
(MSC) 118.
[0026] A packet data service node may fall in one of several
states, e.g., active or connected state, dormant state, and null or
inactive state. In the active or connected state, an active traffic
channel exists between the participating MS and the BS or BSC, and
either side may send data. In the dormant state, no active traffic
channel exists between the participating MS and the BSC, but a
point-to-point protocol (PPP) link is maintained between the
participating MS and the PDSN. In the null or inactive state, there
is no active traffic channel between the participating MS and the
BSC, and no PPP link is maintained between the participating MS and
the PDSN.
[0027] After powering up, mobile stations 104 and 106 may request
packet data sessions. As part of establishing a packet data
session, each MS may be assigned an IP address. Each MS may perform
a registration process to notify group call server 102 of the MS's
IP address. Registration may be performed using an IP protocol,
such as session initiation protocol (SIP) over user datagram
protocol (UDP). The IP address of a MS may be used to contact the
MS when the corresponding user is invited into a group call.
[0028] Once a group call is established, mobile stations 104 and
106 and group call server 102 may exchange media and signaling
messages. In one embodiment, media may be exchanged between the
participating mobile stations and the group call server by using
real-time protocol (RTP) over UDP. The signaling messages may also
be exchanged by using a signaling protocol over UDP.
[0029] Group communication system 100 performs several different
functions in order to provide group call services. The functions
that relate to the user side include user registration, group call
initiation, group call termination, sending alerts to group
participants, late join to a group call, talker arbitration, adding
members to a group, removing members from a group, un-registering a
member, and user and/or device authentication. The functions that
relate to system preparation and operation include administration
and provisioning, scalability, and reliability. These functions are
described in detail in the copending patent application, U.S.
patent application Ser. No. 10/076,726, filed Feb. 14, 2002, which
is assigned to the same assignee and incorporated herein by
reference in its entirety.
[0030] FIG. 2 is a simplified block diagram of an embodiment of
base station 204 and mobile station 206, which are capable of
implementing various disclosed embodiments. For a particular
communication, voice data, packet data, and/or messages may be
exchanged between base station 204 and mobile station 206, via an
air interface 208. Various types of messages may be transmitted,
such as messages used to establish a communication session between
the base station and mobile station, registration and paging
messages, and messages used to control a data transmission (e.g.,
power control, data rate information, acknowledgment, and so on).
Some of these message types are described in further detail
below.
[0031] For the reverse link, at mobile station 206, voice and/or
packet data (e.g., from a data source 210) and messages (e.g., from
a controller 230) are provided to a transmit (TX) data processor
212, which formats and encodes the data and messages with one or
more coding schemes to generate coded data. Each coding scheme may
include any combination of cyclic redundancy check (CRC),
convolutional, turbo, block, and other coding, or no coding at all.
The voice data, packet data, and messages may be coded using
different schemes, and different types of messages may be coded
differently.
[0032] The coded data is then provided to a modulator (MOD) 214 and
further processed (e.g., covered, spread with short PN sequences,
and scrambled with a long PN sequence assigned to the user
terminal). The modulated data is then provided to a transmitter
unit (TMTR) 216 and conditioned (e.g., converted to one or more
analog signals, amplified, filtered, and quadrature modulated) to
generate a reverse link signal. The reverse link signal is routed
through a duplexer (D) 218 and transmitted via an antenna 220 to
base station 204.
[0033] At base station 204, the reverse link signal is received by
an antenna 250, routed through a duplexer 252, and provided to a
receiver unit (RCVR) 254. Base station 204 may receive registration
information and status information, e.g., mobile station mobility
rate, from mobile station 206. Receiver unit 254 conditions (e.g.,
filters, amplifies, down converts, and digitizes) the received
signal and provides samples. A demodulator (DEMOD) 256 receives and
processes (e.g., despreads, decovers, and pilot demodulates) the
samples to provide recovered symbols. Demodulator 256 may implement
a rake receiver that processes multiple instances of the received
signal and generates combined symbols. A receive (RX) data
processor 258 then decodes the symbols to recover the data and
messages transmitted on the reverse link. The recovered
voice/packet data is provided to a data sink 260 and the recovered
messages may be provided to a controller 270. Controller 270 may
include instructions for determining a paging area, paging a group
of mobile stations, and sending information to the mobile stations.
The processing by demodulator 256 and RX data processor 258 are
complementary to that performed at mobile station 206. Demodulator
256 and RX data processor 258 may further be operated to process
multiple transmissions received via multiple channels, e.g., a
reverse fundamental channel (R-FCH) and a reverse supplemental
channel (R-SCH). Also, transmissions may be simultaneously from
multiple mobile stations, each of which may be transmitting on a
reverse fundamental channel, a reverse supplemental channel, or
both.
[0034] On the forward link, at base station 204, voice and/or
packet data (e.g., from a data source 262) and messages (e.g., from
controller 270) are processed (e.g., formatted and encoded) by a
transmit (TX) data processor 264, further processed (e.g., covered
and spread) by a modulator (MOD) 266, and conditioned (e.g.,
converted to analog signals, amplified, filtered, and quadrature
modulated) by a transmitter unit (TMTR) 268 to generate a forward
link signal. The forward link signal is routed through duplexer 252
and transmitted via antenna 250 to mobile station 206. Forward link
signals include paging signals.
[0035] At mobile station 206, the forward link signal is received
by antenna 220, routed through duplexer 218, and provided to a
receiver unit 222. Receiver unit 222 conditions (e.g., down
converts, filters, amplifies, quadrature modulates, and digitizes)
the received signal and provides samples. The samples are processed
(e.g., despreaded, decovered, and pilot demodulated) by a
demodulator 224 to provide symbols, and the symbols are further
processed (e.g., decoded and checked) by a receive data processor
226 to recover the data and messages transmitted on the forward
link. The recovered data is provided to a data sink 228, and the
recovered messages may be provided to controller 230. Controller
230 may include instructions for determining the number of pilot
signals in an active set, adding new pilots in the active set,
moving pilot signals from a list to another list, registering
mobile station 206, and providing the registration information to
the base station 204.
[0036] The group call service (GCS) may allow one user to talk to a
group of users in a half-duplex or full-duplex mode. In the former
case, because only one person may be permitted to talk at a time,
the permission to talk may be moderated by the infrastructure. In
such systems, a user may request permission to talk by pressing a
"push-to-talk" button (PTT), for example. The system may arbitrate
the requests received from multiple users and, through a
contention-resolution process, the system may choose one of the
requesters according to a predetermined algorithm. The system may
then notify the chosen user that the user has permission to talk.
The system may transparently dispatch the user's traffic
information, such as voice and/or data, from the authorized talker
to the rest of the group members, who may be considered
"listeners." The voice and/or data traffic in GCS may be different
from the classical one-to-one phone call, and a priority may be
placed on some conversations.
[0037] FIG. 3 illustrates a group call arrangement for showing how
mobile stations (MSs) 302, 304, and 306 interact with a group call
server 308. Multiple group call servers may be deployed as desired
for large-scale groups. In FIG. 3, when MS 302 has permission to
transmit media to other members of the group, MS 302 is known as
the talker and may transmit media over an established channel. When
MS 302 is designated as the talker, the remaining participants, MS
304 and MS 306, may not have permission to transmit media to the
group. Accordingly, MS 304 and MS 306 are designated as listeners.
As described above, MSs 302, 304, and 306 are connected to group
call server 308, using at least one channel. In one embodiment,
channels 310, 312, and 314 may include a session initiation
protocol (SIP) channel, a media-signaling channel, and a media
traffic channel.
[0038] FIG. 4 illustrates one embodiment for the group call server
102 operating in the system of FIG. 1. The group call server
includes antennas 402, 404 for transmitting and receiving data.
Antenna 402 is coupled to the receiver circuitry 406 and antenna
404 is coupled to the transmit circuitry 408. Communication bus 410
provides a common connection among other modules in FIG. 4.
Communication bus 410 is further coupled to memory unit 412. Memory
412 stores computer readable instructions for a variety of
operations and functions performed by the group call server. The
processor 414 performs the instructions stored in memory 412.
[0039] FIG. 5 illustrates a message-flow diagram showing a group
call setup, according to one embodiment. A user who wishes to
initiate a group call selects one or more target users, one or more
pre-defined groups, or a combination of the two and may depress the
push-to-talk (PTT) button on a MS. The caller's MS may be in a
dormant packet data session when the caller initiates the group
call. The caller's MS then sends a group call request 502 to the
group call server to setup the group call. The group call request
may be transmitted regardless of whether the caller's MS has a
dedicated traffic channel or not. After the group call request is
sent, if the caller's MS is in dormant packet data session, the
caller's MS initiates the process of re-establishing its dedicated
traffic channel and prepare the packet data session for media
activity.
[0040] When the group call server receives the group call request,
the group call server expands the pre-defined groups, if any is
specified in the received group call request, into a list of group
members. The group call server retrieves location information for
the desired group members. The group call server also determines if
the target group is already running in the system.
[0041] After the group call server locates at least one of the
group members, the group call server sends an announcement 504 back
to the caller's MS indicating that the group call is being set up.
At this point, the caller's MS optimistically grants the caller's
request to talk. The caller's MS starts buffering the received
media for future transmission to the group call server. The group
call server uses the location information of the target listeners'
mobile stations to send out announcements 506 to the target
listeners' Mobile stations. Sending the announcements triggers the
packet data sessions of the target listeners' mobile stations to
come out of dormancy and to re-establish their traffic
channels.
[0042] The "instant response" relates to the response time it takes
for the group call server to respond to a PTT or group call
request. The goal for responding to the PTT or group call request
is to consistently respond to the request within a predetermined
time period, e.g., one second or less. In many cases, when a caller
requests to setup a group call, the caller's packet data session is
dormant, meaning that no dedicated traffic channel exists.
Re-establishing dedicated traffic channels may take considerable
time.
[0043] In one embodiment, group communication system 100 (FIG. 1)
supports both chat-room and ad-hoc models for group call services.
In the chat-room model, groups are predefined, which may be stored
on the group call server. The predefined groups, or nets, may be
public, implying that the group has an open member list. In this
case, each group member is a potential participant in a group call.
The group call is started when a first group member starts to
initiate a group call. The call remains running for a
pre-determined time period, which may be configured by the service
provider. During a group call, the group members may specifically
request to join or leave the call. During periods of talk
inactivity, the group call may be brought into a group dormant
state until a group member requests permission to talk. When
operating in the chat-room model, group members, also known as net
members, communicate with one another using a mobile station
assigned to each net member. The term "net" denotes a group of
members authorized to communicate with each other.
[0044] In the ad-hoc model of group call services, however, groups
may be defined in real-time and have a closed member list
associated with each group. A closed member list may specify which
members are allowed to participate in the group call. The member
list may not be available to others outside of the closed member
list, and may only exist for the life of the call. Ad-hoc group
definitions may not be stored in the group call server. The
definitions may be used to establish the group call and released
after the call has ended. An ad-hoc group may be formed when a
caller selects one or more target members and generates a group
call request, which is sent to the group call server to start the
call. The group call server may send a notification to the target
group members that they have been included in the group. The group
call server may automatically join the target members into the
group call, i.e., no action may be required from the target
members. When an ad-hoc call becomes inactive, the group
communication server may "tear down" the call and free the
resources assigned to the group, including the group definition
used to start the call.
[0045] Network-Originated Call-Signaling Messages
[0046] In one embodiment, after receiving the floor-control
request, the group call server may burst media-signaling messages
to a group of dormant target Mobile stations and trigger the
dormant target Mobile stations to re-establish their dedicated
traffic channels. In one embodiment, the packet control function
(PCF) receives a small amount of information, e.g., packet data,
from the packet data serving node (PDSN), which may be destined for
a dormant target MS. The PCF may choose to send the information to
the base station controller (BSC) in a special form. In one
embodiment, the special form includes short data burst (SDB)
format, as specified in the TIA/EIA/IS-707-A-2, "Data Service
Option Standard for Spread Spectrum Systems," Addendum 2, dated
June 2000 (IS-707-A-2). The TIA/EIA/IS-2001-A, "Interoperability
Specification (IOS) for cdma2000 Access Network Interfaces," dated
August 2001 (IS-2001-A) standard defines several options for the
BSC to deliver SDB messages to target Mobile stations.
[0047] According to the IS-2001-A standard, for example, when a
small amount of data destined for a dormant target MS is received
at the PCF, the PCF may choose to send the received data to the BSC
in SDB format. If the BSC determines that short data bursts may be
used to deliver the data to the dormant target MS, the BSC may send
the data directly to the dormant target MS over a signaling
channel. The BSC may also send the data to the MSC for delivery to
the dormant target MS via an application data delivery service
(ADDS) Page. The data may be delivered to the MSC using a BSC
service request/response procedure. If the BSC is unsuccessful in
delivering the SDB data to the dormant target MS on its own, the
BSC may choose to send the data to the MSC for delivery to the
dormant target MS via the ADDS Page procedure.
[0048] FIG. 6 shows a call-flow procedure for delivering data to a
target MS, according to one embodiment. The packet data session is
in the dormant state 602 with PPP connected. The PDSN sends packet
data 604 to the PCF on the existing PPP connection associated with
the target MS. The PCF sends the packet data 606 to the BSC. The
PCF also buffers the packet data. The BSC acknowledges receiving
the data packets from the PCF by returning an acknowledge message
608, which includes an indication that the BSC attempts to send the
data to the target MS. The PCF then discards the data that it had
buffered.
[0049] The BSC sends the packet data directly to the target MS or,
alternatively, the BSC uses an ADDS Page procedure to deliver the
packet data, e.g., in SDB form, to the target MS. If the BSC
directly sends the packet data 610 to the target MS, the target MS
sends an acknowledgement 612 in response to receiving the data. If
an acknowledgement is not received from the target MS, the BSC may
choose not to send the packet data or may request the MSC to
deliver the packet data via ADDS Page procedure.
[0050] If the BSC could not successfully send the packet data 610
to the target MS, the BSC sends a "BSC service request" 614, which
contains the packet data, to the MSC. The MSC acknowledges
receiving the BSC service request message by sending a "BSC service
response" 616 to the BSC. The MSC then sends an ADDS Page message
618 to the BSC for delivering the packet data to the target MS. If
the MSC sends the packet data, the MSC specifies the "data type
field" in the ADDS Page to "SDB." The ADDS Page message contains
the location information for the target MS. Accordingly, the BSC
forwards the data 620, e.g., in SDB form, to the target MS. The
target MS sends an acknowledgement message 622 after receiving the
data from the BSC. If the MSC had requested in the ADDS Page
message, the BSC returns an ADDS Page acknowledgement message 624
to the MSC, after receiving the acknowledgement message from the
target MS. The BSC also sends an update message 626 to the PCF to
indicate successful transmission of the data to the target MS. The
PCF responds 628 to the BSC with an update acknowledge message. The
PCF sends a registration request 630 to the PDSN, which responds
with a registration reply message 632.
[0051] Having the BSC directly deliver the packet data to the
target MS may minimize the delay, but the target MS may not receive
the data because the target MS may have moved out of the BSC's
paging area by the time the data arrive. Since the MSC maintains
location information for the target MS, the ADDS Page data delivery
process ensures that the target MS receives the data. In one
embodiment, the BSC may cache location information for the target
MS, which may be used by the BSC when there is data destined for
the target MS. Using the location information cached at the BSC
eliminates the delay due to having the BSC to request the MSC to
send the ADDS Page. This process provides assured delivery of the
data to the target MS based on the saved location information.
[0052] On embodiment of cashing location information for the mobile
stations is illustrated in FIG. 7. The BSC caches 702, 704 the
target MS's location information after the BSC receives a page
response 706 from the target MS or receives a "location update
accept" message 708 from the MSC. The page response message
received from the target MS may include a cell identifier field
that specifies the location, e.g., a cell location area code (LAC),
of the target MS. In one embodiment, the BSC may obtain the target
MS's location information from the target MS's registration
message. For example, there are several different types of
registration defined by the TIA/EIA/IS-2000.5-A, "Upper Layer
(Layer 3) Signaling Standard for cdma2000 Spread Spectrum Systems,"
dated November 2000 (IS-2000 standard). Any of these registration
types may provide the BSC information about the location of the
target MS. The BSC may update the cached location information if
the BSC receives a page response, a registration response, an
origination message, or other signaling messages that provide the
current location information for the target MS.
[0053] Network Configurations
[0054] Each PCF in the network may be uniquely identified by a
system identification/network identification/packet zone
identification (SID/NID/PZID) code. When the target MS moves from
one PCF to another PCF, i.e., PCF to PCF handoff, during the
dormant packet data session, the target MS may be required to
re-register to have the PDSN establish an interface with the new
PCF and terminate the existing connection with the old PCF.
[0055] In one embodiment, as shown in FIG. 8, the BSC and the PCF
are co-located. When a packet data arrives at the PCF and the PCF
decides to send the packet data, the target MS may most probably be
under the service area of the same BSC. Otherwise, the target MS
would have been required to re-register and a new connection would
have been established with a different PCF.
[0056] In one embodiment, as shown in FIG. 9, the BSC and the PCF
are not co-located. In FIG. 9, BSC.sub.1 is shown to be fully
interconnected with other BSCs that are connected to the same PCF.
The BSCs that are connected to the same PCF may be interconnected
either via point-to-point link or via a switching network. Unlike
the scenario where the BSC and the PCF are co-located, when the PCF
sends data to BSC.sub.1, BSC.sub.1, may fail in delivering the data
to the target MS because the target MS may have moved outside the
service area of BSC.sub.1, to another BSC's service area. In FIG.
9, for example, the target MS may have been in the service area of
BSC.sub.1, before the packet data session goes dormant, and may
have moved to the service area of BSC.sub.5 when BSC.sub.1,
receives the request from the PCF to deliver data to the target
MS.
[0057] In one embodiment, where the PCF may be co-located with the
BSC, the BSC receives the packet data for transmission to a target
MS, which may be dormant. The BSC may broadcast the packet data to
the cells and/or sectors within the BSC's service area.
Alternatively, to decrease air-link resource consumption, the BSC
may utilize the target MS's location information, which may have
been already cached at the BSC, to broadcast the data to a subset
of cells and/or sectors under the BSC's control.
[0058] In one embodiment, where the PCF may be co-located with the
BSC, as shown in FIG. 10, the BSC receives the packet data 1002
from the PDSN for delivery to a target MS. Before the BSC sends the
packet data 1002 to the target MS, the BSC first buffers the packet
data. The BSC then determines 1004 a paging zone for paging the
target MS, as will be described in more detail herein later. The
BSC then sends out a page message 1006 based on the determined
paging zone under the BSC's service area. If the target MS's
identification information, such as the matching mobile
identification number (MIN) or electronic serial number (ESN),
matches with the identification information specified in the paging
message, the MS sends a paging response 1008 to the BSC. The paging
response provides information about the cell and/or sector the
target MS is located in, which allows the BSC to send the packet
data to the identified cell and/or sector only. The BSC caches 1010
the target MS's location information before sending the packet data
1012 to the target MS. The cached location information may be
refreshed by the next page response, registration response,
origination message, or other signaling messages that provide
location information for the target MS. The cached location
information may be aged out by a timer.
[0059] Cell-based Registration Scheme
[0060] Registration is the process by which the MS notifies the
base station of its location, status, identification, slot cycle,
and other characteristics. The MS informs the base station of its
location and status so that the base station can efficiently page
the MS when establishing a MS-terminated call. While the MS is in
idle state, the MS may perform registration when an idle handoff
occurs. An idle handoff occurs when a MS has moved from the
coverage area of one base station into the coverage area of another
base station during the MS idle state. If the MS detects a pilot
channel signal from another base station that is sufficiently
stronger than that of the current base station, the MS determines
that an idle handoff should occur.
[0061] Idle handoff is the act of transferring reception of the
paging channel, broadcast control channel or the forward common
control channel from one base station to another base station, when
the MS is in the idle state. The MS in an idle state determines
that an idle handoff is needed if the pilot signal strength of the
new cell is certain decibels greater than the pilot signal in its
Active Set.
[0062] When the MS transits from other states to the idle state,
the MS may initialize two lists of cells. The first list is named
CURRENT_CELL_LIST and the second list is named PREV_CELL_LIST. As
the MS performs an idle handoff, the mobile station adds the new
cell's identification information into the CURRENT_CELL_LIST if the
new cell is not already identified in the list. The MS may obtain
the new cell's information by listening to the broadcasted overhead
messages.
[0063] In one embodiment, if the number of cells in the
CURRENT_CELL_LIST list reaches a predetermined limit, e.g.,
MAX_NUM_CELLS, the MS performs a registration and copies the
entries in the CURRENT_CELL_LIST, except the last entry, into the
PREV_CELL_LIST. Thus, the size of the PREV_CELL_LIST is equal to
the predetermined limit, e.g., MAX_NUM_CELLS, less one.
[0064] FIG. 11 illustrates a registration process, according to one
embodiment. The CURRENT_CELL_LIST includes at least the
identification information of the cell in which the MS last
registered, 1102. As the MS detects a new pilot signal that may be
added to the active set, the MS adds the identification information
of the new cell in the CURRENT_CELL_LIST, in step 1104, if the cell
is not already identified in the CURRENT_CELL_LIST. In step 1106,
the MS determines whether the number of cells identified in the
CURRENT_CELL_LIST has reached the predetermined limit, e.g.,
MAX_NUM_CELLS. If the number of cells in the CURRENT_CELL_LIST has
reached the predetermined limit, the MS performs a registration, in
step 1108, and moves the identification information of the cells in
the CURRENT_CELL_LIST, except the last entered cell in which the MS
registered, to the PREV_CELL_LIST, in step 1110.
[0065] In one embodiment, the cell layout is shown as in FIG. 12.
Letting the predetermined limit, MAX_NUM_CELLS, to be three and the
MS's trajectory from cell to cell to be A1.fwdarw.B2.fwdarw.C3, and
assuming the cell in which the mobile last registered is A1, 1202,
the CURRENT_CELL_LIST would contain cell {A1}. After the MS detects
the pilot signal of cell B2, 1204, and adds cell B2 to the
CURRENT_CELL_LIST, the latter contains cells {A1, B2}. As the MS
moves toward cell C3, 1206, the MS detects and adds cell C3 to the
CURRENT_CELL_LIST, which now contains cells {A1, B2, C3}. Now,
since the number of cells identified in the CURRENT_CELL_LIST
equals the predetermined limit, e.g., three, the MS performs a
registration with the network and moves the cells {A1, B2} from the
CURRENT_CELL_LIST to the PREVIOUS_CELL_LIST.
[0066] Paging a mobile station includes the act of seeking the
mobile station when a call is to be placed to that mobile station.
To conserve system capacity, reduce service cost, and save battery
life, it is desirable to minimize paging area to reduce the paging
channel load. The paging area may be configured, e.g., predefined
or dynamically determined, for a given BSC. The paging area may be
different for different BSCs. The BSC pages the target MS in the
configured paging area. If the target MS cannot be located in the
configured paging area of the BSC, the data may be sent to a
neighboring BSC for delivering to the target MS. Therefore, each
BSC need not to unnecessarily page in a large area. If the target
MS cannot be located in the paging area of the BSCs connected to a
mobile station controller (MSC), the data may be sent to the MSC
for delivering to the target MS, if the MSC could locate the target
MS.
[0067] FIG. 13 shows a paging scheme, according to one embodiment.
In step 1302, the BSC receives registration information from the
target MS, which is located in the cell X. When the BSC receives
information, e.g., data, voice, image, text, video, or any
combination thereof, for delivery to the target MS, in step 1304,
the BSC pages the target MS based on a paging area, which may be a
predefined area or a dynamically determined area. In step 1306, the
BSC configures the paging area based on a certain number of cells
from or around the cell in which the target MS last registered. For
example, the paging area may include the cells that fall within an
area that is centered at cell X and extended by a predetermined
number of cells, e.g., MAX_NUM_CELLS less one.
[0068] After the BSC pages the target MS based on the configured
paging area, the BSC waits for a paging response from the target
MS, in step 1308. If the BSC could locate the target MS from the
paging response, the BSC sends the information destined for the
target MS to the target MS, in step 1310. However, if the BSC could
not locate the target MS from the paging response, the BSC requests
a neighboring BSC to locate the target MS, which may be by the same
paging scheme discussed above. If the neighboring BSC locates the
target MS, in step 1312, the BSC sends the information destined for
the target MS to the neighboring BSC for delivery to the target MS,
in step 1314.
[0069] If none of the BSCs connected to the MSC could locate the
target MS, the MSC is requested to locate the target MS, which may
be based on a flood paging scheme. If the MSC locates the target
MS, in step 1316, the BSC holding the information destined for the
target sends the information to the MSC to for delivery to the
target MS, in step 1318. In case the MSC could not locate the
target MS, the MS may not be found due to being turned off or being
out of service 1320.
[0070] For example, letting the trajectory of the target MS from
cell to cell to be "A.fwdarw.B
C.fwdarw.D.fwdarw.E.fwdarw.D.fwdarw.C.fwdarw.B.fwd- arw.F," the
predetermined limit, e.g., MAX_NUM_CELLS, to be three, and assuming
the cell in which the MS last registered is cell A, the
CURRENT_CELL_LIST would contain cell {A}. After the MS detects and
adds cell B to the CURRENT_CELL_LIST, the latter contains cells {A,
B}. As the MS moves toward cell C, the MS detects and adds cell C
to the CURRENT_CELL_LIST, making it to contain now cells {A, B, C}.
Since the number of cells in the CURRENT_CELL_LIST equals to the
predetermined limit, e.g., 3, the MS performs a registration in
cell C and moves cells {A, B} from the CURRENT_CELL_LIST to the
PREVIOUS_CELL_LIST.
[0071] As the MS moves through cell D, and then to cell E, the MS
adds cells D and E to the CURRENT_CELL_LIST, making it to contain
now cells {C, D, E}. Since the number of cells in the
CURRENT_CELL_LIST equals the predetermined limit, e.g., three, the
MS performs a registration in cell E and moves cells {C, D} from
the CURRENT_CELL_LIST to the PREVIOUS_CELL_LIST.
[0072] As the MS moves back to cell D, and then to C, the MS does
not add cells D and C to the CURRENT_CELL_LIST, because these cells
are already included in current PREVIOUS_CELL_LIST. However, when
the MS moves back to cell B, the MS adds the identification
information of the cell B to the CURRENT_CELL_LIST, because cell B
is not included in the PREVIOUS_CELL_LIST, which now includes cells
C and D.
[0073] As the MS moves through a new cell F, the MS detects and
adds cell F to the CURRENT_CELL_LIST, which now contains cells {E,
B, F}. Since the number of cells in the CURRENT_CELL_LIST equals
the predetermined limit of three, e.g., MAX_NUM_CELLS, the MS
performs a registration in cell F and moves cells {E, B} from the
CURRENT_CELL_LIST to the PREVIOUS_CELL_LIST.
[0074] In one embodiment, where the PCF may not be co-located with
the BSC, the BSC receives a request from the PCF to send the packet
data to the target MS. The BSC determines if the BSC has cached
location information for the target MS. If the BSC had cached
location information for the target MS, which allows the BSC to
perform assured data delivery, the BSC sends the data to the target
MS, according to the cached location information. Otherwise, if the
BSC did not have location information for the target MS, the BSC
may send a page message to a predetermined paging zone to locate
the target MS. If BSC could locate the target MS, the BSC then
sends the data received from the PCF to the target MS. However, if
the BSC could not locate the target MS in the predetermined paging
zone, the BSC may send the data to a neighboring BSC, which may be
connected to the same MSC, so that one of the neighboring BSCs that
has location information for the target MS, or can locate the
target MS, transmits the information to the target MS. The BSC that
has cached location information for the target MS, or can locate
the target MS, delivers the data to the target MS. If no BSC has
location information for the target MS, nor can locate the target
MS, the data may be sent to the MSC to be delivered to the target
MS, e.g., via flood paging. The MSC may not locate the target MS,
due to the target MS being turned off or out of service. Therefore,
the disclosed embodiments provide for a significant reduction in
the number of registrations as well as the paging area, thus saving
battery life and paging channel load.
[0075] Those of skill in the art would understand that information
and signals may be represented using any of a variety of different
technologies and protocols. For example, data, instructions,
commands, information, signals, bits, symbols, and chips that may
be referenced throughout the above description may be represented
by voltages, currents, electromagnetic waves, magnetic fields or
particles, optical fields or particles, or any combination
thereof.
[0076] Those of skill would further appreciate that the various
illustrative logical blocks, modules, circuits, and algorithm steps
described in connection with the embodiments disclosed herein may
be implemented as electronic hardware, computer software, or
combinations of both. To clearly illustrate this interchangeability
of hardware and software, various illustrative components, blocks,
modules, circuits, and steps have been described above generally in
terms of their functionality. Whether such functionality is
implemented as hardware or software depends upon the particular
application and design constraints imposed on the overall system.
Skilled artisans may implement the described functionality in
varying ways for each particular application, but such
implementation decisions should not be interpreted as causing a
departure from the scope of the present invention.
[0077] The various illustrative logical blocks, modules, and
circuits described in connection with the embodiments disclosed
herein may be implemented or performed with a general purpose
processor, a digital signal processor (DSP), an application
specific integrated circuit (ASIC), a field programmable gate array
(FPGA) or other programmable logic device, discrete gate or
transistor logic, discrete hardware components, or any combination
thereof designed to perform the functions described herein. A
general-purpose processor may be a microprocessor, but, in the
alternative, the processor may be any conventional processor,
controller, microcontroller, or state machine. A processor may also
be implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
[0078] The steps of a method or algorithm described in connection
with the embodiments disclosed herein may be embodied directly in
hardware, in a software module executed by a processor, or in a
combination of the two. A software module may reside in RAM memory,
flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a
hard disk, a removable disk, a MS-ROM, or any other form of storage
medium known in the art. An exemplary storage medium is coupled to
the processor, such that the processor can read information from,
and write information to, the storage medium. In the alternative,
the storage medium may be integral to the processor. The processor
and the storage medium may reside in an ASIC. The ASIC may reside
in a user terminal. In the alternative, the processor and the
storage medium may reside as discrete components in a user
terminal.
[0079] The description of the disclosed embodiments is provided to
enable any person skilled in the art to make or use the present
invention. Various modifications to these embodiments may be
readily apparent to those skilled in the art, and the generic
principles defined herein may be applied to other embodiments,
e.g., in an instant messaging service or any general wireless data
communication applications, without departing from the spirit or
scope of the invention. Thus, the present invention is not intended
to be limited to the embodiments shown herein but is to be accorded
the widest scope consistent with the principles and novel features
disclosed herein.
* * * * *