Title: Method and apparatus for data transmission within a communication system
Abstract: When the user is actively transmitting/receiving or has recently transmitted/received on the RF channel, the user is referred to as being in an "active" state. Typically, if the user is in the active state, and neither sends nor receives data for a timer period greater than a threshold, then the user is transitioned off of the RF channel (e.g. transitioned from active to dormant). Once a transition to the dormant state has occurred, the continued transmission or re-transmission of data over an RF channel can result in a delay in re-accessing the RF channel. In order to address this problem, the idle-timer threshold is dynamically adjusted based on a communication system statistic to increase system performance.
Patent Number: 6,871,074 Issued on 03/22/2005 to Harris, et al.
| Inventors:
|
Harris; John M. (Chicago, IL);
Fleming; Philip J. (Glen Ellyn, IL);
Argyropoulos; Yiannis (East Lansing, MI)
|
| Assignee:
|
Motorola, Inc. (Schaumburg, IL)
|
| Appl. No.:
|
057365 |
| Filed:
|
January 25, 2002 |
| Current U.S. Class: |
455/452.1; 455/453; 455/450 |
| Intern'l Class: |
H04Q 007//20 |
| Field of Search: |
455/450,451,452.1,453,509,512,574,343.1,343.2,343.4,528
|
References Cited [Referenced By]
U.S. Patent Documents
| 6442652 | Aug., 2002 | Laboy et al. | 711/138.
|
| 6529497 | Mar., 2003 | Hjelm et al. | 370/347.
|
| 2002/0132586 | Sep., 2002 | Chen et al. | 455/69.
|
| 2002/0172178 | Nov., 2002 | Suzuki et al.
| |
| 2002/0198012 | Dec., 2002 | Vukovic et al. | 455/509.
|
| Foreign Patent Documents |
| 198 45 071 | Apr., 2000 | DE.
| |
| 0 830 040 | Mar., 1998 | EP.
| |
| WO 96/37079 | Nov., 1996 | WO.
| |
| WO 00/01173 | Jan., 2000 | WO.
| |
| WO 01/20930 | Mar., 2001 | WO.
| |
Other References
Keshav, Srinivasan et al. "An Empirical Evaluation of Virtual Circuit
Holding Time Policies in IP-Over-ATM Networks." IEEE Journal on Selected
Areas of Communications, vol. 13, No. 8, Oct. 1995, pp. 1371-1382.
|
Primary Examiner: Chin; Vivian
Assistant Examiner: Dao; Minh D
Attorney, Agent or Firm: Haas; Kenneth A., Pace; Lalita W.
Claims
What is claimed is:
1. A method for data transmission within a wireless communication system,
the method comprising the steps of:
determining that data transmission to a remote unit needs to take place;
determining one of a length of time that a current data transmission call
of a remote unit has taken place and a link speed for a current data
transmission call of a remote unit; and
adjusting an idle-timer threshold based on the one of a length of time that
the current data transmission call of the remote unit has taken place and
the link speed for the current data transmission call of the remote unit,
wherein the current data transmission call is dropped if there exists no
data transmission for a period of time greater than the idle-timer
threshold.
2. A method for data transmission within a communication system, the method
comprising the steps of:
receiving data to be transmitted;
transmitting the data over an RF channel to a remote unit;
detecting a pause in the received data;
determining a time period for the pause in the received data;
determining one of a length of time that a current data transmission call
of a remote unit has taken place and a link speed for a current data
transmission call of a remote unit;
adjusting an idle-timer threshold based on the one of a length of time that
the current data transmission call of the remote unit has taken place and
the link speed for the current data transmission call of the remote unit;
comparing the time period to the idle-timer threshold; and
discontinuing transmission of the data if the time period is greater than
the idle-timer threshold, otherwise continuing to transmit the data over
the RF channel.
3. An apparatus comprising:
data transmission circuitry for transmitting over an RF channel to a remote
unit; and
an idle timer coupled to the data transmission circuitry, the idle timer
detecting a time period that data transmission ceases; determines one of a
length of time that a current data transmission call of a remote unit has
taken place and a link speed for a current data transmission call of the
remote unit, and adjusting an idle-timer threshold based on the one of a
length of time that the current data transmission call of the remote unit
has taken place and the link speed for the current data transmission call
of the remote unit, wherein an RF channel is dropped if there exists no
data transmission for a period of time greater than the idle-timer
threshold.
Description
FIELD OF THE INVENTION
The present invention relates generally to cellular communication systems
and, in particular, to data transmission within a cellular communication
system.
BACKGROUND OF THE INVENTION
Communication systems are well known and consist of many types, including
land mobile radio, cellular radiotelephone, personal communication
systems, and other communication system types. Within a communication
system, transmissions are conducted between a transmitting device and a
receiving device over a communication resource, commonly referred to as a
communication channel. Data transmission within a cdma2000 communication
system takes place by assigning the remote unit a data channel (referred
to as a radio-frequency, or RF channel) and transmitting data utilizing
the RF channel.
When the user is actively transmitting/receiving or has recently
transmitted/received on the RF channel, the user is referred to as being
in an "active" state. Typically, if the user is in the active state, and
neither sends nor receives data for a period of time, then the user is
transitioned off of the RF channel (transitioned from active to dormant).
The ability to quickly re-access an RF channel may be limited due to the
transition delay from active to dormant state. In other words, once an RF
channel is dropped, any subsequent transmission/re-transmission of data
over an RF channel can result in delay in re-accessing the RF channel.
Therefore, a need exists for a method and apparatus for data transmission
within a communication system that minimizes the occurrence of dormant to
active transitions and results in more efficient use of the data channel
than with prior-art methods.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a communication system in accordance with the
preferred embodiment of the present invention.
FIG. 2 is a flow chart showing operation of the base station of FIG. 1 in
accordance with a first embodiment of the present invention.
FIG. 3 is a flow chart showing operation of the base station of FIG. 1 in
accordance with a second embodiment of the present invention.
FIG. 4 is a flow chart showing operation of the base station of FIG. 1 in
accordance with a third embodiment of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
In order to address the above-mentioned problem, in the preferred
embodiment of the present invention an idle-timer threshold is dynamically
adjusted based on a communication system statistic to increase system
performance. More particularly, during a data call, the idle-timer
threshold is changed in order to increase the probability of not dropping
the data call when data remains to be transmitted or will need to be
transmitted in the near future.
The present invention encompasses a method for data transmission within a
wireless communication system. The method comprises the steps of
determining that data transmission needs to take place, determining a
communication system statistic, and adjusting an idle-timer threshold
based on the communication system statistic. In the preferred embodiment
of the present invention a data call is dropped if there exists no data
transmission for a period of time greater than the idle-timer threshold.
The present invention additionally encompasses a method for data
transmission within a communication system. The method comprises the steps
of receiving data to be transmitted, transmitting the data over an RF
channel, and detecting a pause in the received data. A time period is
determined for the pause in the received data and a communication system
statistic is also determined. An idle-timer threshold is then adjusted
based on the communication system statistic. The time period for cessation
of data is then compared to the idle-timer threshold and transmission of
the data is discontinued if the time period is greater than the idle-timer
threshold.
The present invention additionally encompasses an apparatus. The apparatus
comprises data transmission circuitry for transmitting over an RF channel,
and an idle timer coupled to the data transmission circuitry. The idle
timer detects a time period that data transmission ceases and determines a
communication system statistic. The idle-timer threshold is adjusted based
on the communication system statistic. The RF channel is dropped if there
exists no data transmission for a period of time greater than the
idle-timer threshold.
FIG. 1 illustrates wireless communication system 100 in accordance with the
preferred embodiment of the present invention. In the preferred embodiment
of the present invention, communication system 100 utilizes the next
generation CDMA architecture as described in the cdma2000 International
Telecommunication Union-Radiocommunication (ITU-R) Radio Transmission
Technology (RTT) Candidate Submission document (cdma2000), but in
alternate embodiments communication system 100 may utilize other analog or
digital cellular communication system protocols such as, but not limited
to, the next generation Global System for Mobile Communications (GSM)
protocol, the CDMA system protocol as described in "Personal Station-Base
Station Compatibility Requirements for 1.8 to 2.0 GHz Code Division
Multiple Access (CDMA) Personal Communication Systems" (American National
Standards Institute (ANSI) J-STD-008), or the European Telecommunications
Standards Institute (ETSI) Wideband CDMA (W-CDMA) protocol. In the
preferred embodiment of the present invention, all network elements are
available from Motorola, Inc. (Motorola Inc. is located at 1301 East
Algonquin Road, Schaumburg, Ill. 60196). It is contemplated that network
elements within communication system 100 are configured in well known
manners with processors, memories, instruction sets, and the like, which
function in any suitable manner to perform the function set forth herein.
As shown, base station 101 is communicating with remote, or mobile unit 102
via downlink communication signal 106. Additionally, base station 101
comprises idle timer 105, logic circuitry 103, and data transmission
circuitry 104, which in the preferred embodiment of the present invention
comprises RF channel circuitry as described in cdma2000. Although a single
data transmission circuit 104 is shown, one of ordinary skill in the art
will recognize that multiple data transmission circuits exist within base
station 101.
Data transmission from base station 101 in accordance with the preferred
embodiment of the present invention occurs as follows: During time periods
where remote unit 102 is not actively communicating to base station 101,
remote unit 102 is in a suspended state, actively or periodically
monitoring a forward control channel or paging channel (not shown) for
notification of any pending transmission by base station 101. While in
this suspended state, base station 101 is also waiting for transmission
from remote unit 102. In particular, paging channel circuitry is utilized
to send messages to remote unit 102 indicating pending downlink
transmissions. In the preferred embodiment of the present invention,
paging channels circuitry is circuitry such as described in IS-95A Section
7.1.3.4, 7.6.2 and Section 7.7.2.
Data destined to remote unit 102 enters logic circuitry 103, and logic
circuitry 103 determines that a transmission to remote unit 102 needs to
take place and determines if data transmission circuitry 104 is available
for utilization. Remote unit 102 is placed in an active state where it is
assigned a traffic, or fundamental channel (not shown). In particular,
base station 101 notifies remote unit 102 of spreading codes (Walsh Codes)
utilized by the fundamental and RF channels and an assigned data rate of
the RF channel. Additionally, initial power control takes place at this
point utilizing the fundamental channel as described in IS-95A sections
6.1.2 and 6.6.3.1.1.1.
Once at the appropriate power level, and when an RF channel becomes
available, remote unit 102 enters an active state, where communication
utilizing the RF channel (i.e., data transmission) occurs.
Transmission on the RF channel may stop, inter alia, for two reasons. A
first reason for transitioning to dormant state is because, all data has
been communicated to and from remote unit 102. A second reason for
transitioning to dormant state is because the time since the last
transmission is greater than a threshold. More particularly, once data
transmission ceases, idle timer 105 begins to track the time period
inactivity. If the time period of inactivity surpasses a threshold
(idle-timer threshold), then the RF, or data channel 106 is dropped and
remote unit 102 is placed in dormant state.
As discussed above, once a transition to the dormant state has occurred,
the continued transmission or re-transmission of data over an RF channel
can result in a delay in re-accessing the RF channel. In order to address
this problem, the idle-timer threshold is dynamically adjusted based on a
communication system statistic. In particular, the idle-timer threshold is
dynamically adjusted during data transmission to increase system
performance.
Idle Timer Adjusted Based on RF Resources Available
In the preferred embodiment of the present invention, the idle-timer
threshold is adjusted based on a level of RF resources available to base
station 101. (Examples of RF resources in CDMA 2000 include RF
interference capacity, channel elements or data channels available which
in GPRS/UMTS include Temporary Block Flow Identifiers). When fewer data
channels are available, logic circuitry 103 adjusts the idle-timer
threshold downward. Conversely, when there exists sufficient RF resources,
logic circuitry 103 increases the idle-timer threshold.
By adjusting the idle-timer threshold as such, a compromise is made between
user's occupying data channels needlessly after all data transmission
ceases, and using spare resources to improve the user's download. For
example, long idle-timer thresholds result in a higher probability that
the user will not be dropped prior to competing all downloads, at the cost
of potentially keeping the channel occupied after data transmission
ceases. The short idle-timer threshold results in a lower potential of
keeping a channel occupied after each data transmission ceases at the cost
of an increased probability that the user will be moved to dormant state
prior to competing all downloads. When system resources are readily
available, occupying a channel after data transmission ceases has little
impact on system capacity. Therefore, in the preferred embodiment of the
present invention, the idle-timer threshold is adjusted upwards in
proportion to the amount of system resources available as shown in FIG. 2.
FIG. 2 is a flow chart showing operation of base station 101 in accordance
with a first embodiment of the present invention. The logic flow begins at
step 201 where logic circuitry 103 determines if data transmission needs
to take place to remote unit 102. If at step 201 it is determined that
data transmission needs to take place, then the logic flow continues to
step 203, otherwise the logic flow returns to step 201. At step 203, logic
circuitry determines system resources available. In particular, at step
203 a determination is made as to a percentage of RF channels available
for utilization. At step 205 logic unit adjusts the idle-timer threshold
based upon a percentage of RF channels available for utilization. In the
preferred embodiment of the present invention the idle-timer threshold
ranges between 5 seconds and 4 minutes and is adjusted as follows: When
less than 20% of the RF resources are available, then the idle-timer
threshold is set to 5 seconds. When between 20% and 50% of the RF
resources are available, then the idle-timer threshold is set to 30
seconds. When more than 50% of the RF resources are available, then the
idle-timer threshold is set to 240 seconds.
Continuing, at step 207 data transmission begins and the logic flow
continues to step 209 where the idle timer is initialized (set to zero).
At step 211, it is determined if data transmission has ceased and if not
the logic flow continues to step 213 where data transmission continues. If
at step 211 it is determined that data transmission ceases, then the logic
flow continues to step 215 where it is determined if the idle time has
exceeded the idle-timer threshold, and if so, the data channel is dropped
at step 217. More particularly, upon the ceasing of data transmission,
logic unit 103 initiates idle timer 105 to begin tracking the amount of
time since the last data transmission. If it is determined that the time
since the last data transmission is greater than the idle-timer threshold,
then the data channel is dropped (the user is transitioned to dormant
state). It should be noted that in the preferred embodiment of the present
invention the determination that data transmission has ceased is based on
whether or not downlink data transmission has stopped, however in an
alternate embodiment, data transmission may be determined as stopping when
both uplink and downlink data fails to be transmitted over the RF channel.
Continuing, if, at step 215, it is determined that the idle time has not
exceeded the idle-timer threshold then the logic flow continues to step
219 where it is determined the if data transmission has resumed. If the
data transmission has resumed, then the idle timer is re-initialized (step
209) and the logic flow continues to step 211, otherwise the logic flow
simply returns to step 215.
As discussed above, once an RF channel is dropped, the continued
transmission/re-transmission of data over an RF channel can result in a
time consuming procedure of re-accessing an RF channel. By adjusting the
idle-timer threshold based on available system resources, a more efficient
use of the data channel is achieved in that the data channel's probability
of being needlessly dropped when system resources are readily available is
greatly reduced.
Idle-Timer Threshold Based on Length of Call
The length of data calls is generally found to have a decreasing hazard
rate. In practical terms, this means that the longer a data call (e.g.
active interval or PPP session) has lasted thus far, the longer it is
expected to last in the future. As a result of this decreasing hazard rate
of call length, in the preferred embodiment of the present invention when
the active interval length thus far is shorter, a shorter idle-timer
threshold is used. Conversely, when active interval length thus far is
longer, a longer idle-timer threshold is used. This is illustrated in FIG.
3.
FIG. 3 is a flow chart showing operation of base station 101 in accordance
with a second embodiment of the present invention. The logic flow begins
at step 301 where logic circuitry 103 determines if data transmission
needs to take place to remote unit 102. If at step 301, it is determined
that data transmission needs to take place, then the logic flow continues
to step 303, otherwise the logic flow returns to step 301. At step 303,
data transmission begins and the logic flow continues to step 305 and 307
where the call timer 107 and idle timer is initialized (set to zero),
respectively. At step 309 it is determined if data transmission has ceased
and if not the logic flow continues to step 311 where data transmission
continues. If at step 309 it is determined that data transmission ceases,
then the logic flow continues to step 313 where logic circuitry 103
accesses a call timer 107 to determine call length so far (total call time
ths far), and adjusts idle-timer threshold accordingly. For example, in
the case where the amount of RF resources available is constant, for the
first minute of the call the idle-timer threshold is set to 30 seconds. If
the call has lasted between 1 and 5 minutes the idle-timer threshold is
set to 1 minute. After 5 minutes of call length, the idle-timer threshold
is set to 2 minutes.
Continuing, at step 315 it is determined if the idle time has exceeded the
idle-timer threshold, and if so, the data channel is dropped 317. However,
if at step 315 it is determined that the idle time has not exceeded the
idle-timer threshold, then the logic flow continues to step 319 where it
is determined if data transmission has resumed. If the data transmission
has resumed, then the idle timer is re-initialized (step 307) and the
logic flow continues to step 309, otherwise the logic flow simply returns
to step 313.
As discussed above, once an RF channel is dropped, the continued
transmission/re-transmission of data over an RF channel can result in a
delay in re-accessing an RF channel. By adjusting the idle-timer threshold
based on call length, a more efficient use of the data channel is achieved
in that the data channel's probability of being needlessly dropped when
data remains to be transmitted is greatly reduced.
Idle-Timer Threshold Based on Link Speed
The length of data calls are generally found to be positively correlated
with the downlink data rate. In practical terms, this means that calls
with higher data rate downloads typically last longer than calls with
lower data rate downloads (possibly because the user has the capability of
using a wider variety applications). As a result, in the preferred
embodiment of the present invention, when download data rates are low, a
shorter idle-timer threshold is used. Conversely, when download data rates
are high, a longer idle-timer threshold is used. This is illustrated in
FIG. 4.
FIG. 4 is a flow chart showing operation of base station 101 in accordance
with a third embodiment of the present invention. As discussed above, in
the third embodiment of the present invention the idle-timer threshold is
adjusted based on link speed. The logic flow is similar to that described
above with FIG. 3, except that step 313 has been replaced by step 401. In
particular, at step 401, logic circuitry 103 determines a current or
recent maximum downlink speed (e.g., 100 Kb/sec) and adjusts the idle
timer threshold accordingly. The idle-timer threshold is adjusted in the
case where the amount of RF resources available is constant, as follows:
After two minutes of call have elapsed, the idle-timer threshold is set to
30 seconds if the max link speed achieved is less than 9 Kbps. If the link
speed achieved is between 9 Kbps and 50 kbps the idle-timer threshold is
set to one minute. If link speed is above 50 kbps, then the idle-timer
threshold is adjusted to two minutes.
While the invention has been particularly shown and described with
reference to a particular embodiment, it will be understood by those
skilled in the art that various changes in form and details may be made
therein without departing from the spirit and scope of the invention. For
example, although the preferred embodiment of the present invention was
described within a cdma2000 system, one of ordinary skill in the art will
recognize that any communication system may implement the above
procedures. Additionally, although the above description was given with
respect to cellular infrastructure adjusting idle-timer thresholds, one of
ordinary skill in the art will recognize that mobile, or remote units may
adjust idle-timer thresholds as discussed above. It is intended that such
changes come within the scope of the following claims.
*
