Telecommunications – Transmitter and receiver at separate stations – With control signal
Reexamination Certificate
2001-03-16
2003-11-18
Maung, Nay (Department: 2684)
Telecommunications
Transmitter and receiver at separate stations
With control signal
C455S458000, C455S574000, C455S522000, C370S335000, C370S329000
Reexamination Certificate
active
06650873
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to wireless communication systems, and more specifically to a method of adaptively allocating resources at a base station to maximize the wireless communication device standby time in a system using a quick paging channel.
2. Description of the Related Art
FIG. 1
is a block diagram showing a typical modern wireless communication system
10
. The system is comprised of several remote stations
12
and a series of base stations
14
(only one is shown). Mobile stations
12
, such as personal wireless communication handsets, communicate with the base stations
14
over forward link channels
18
and reverse link channels
20
. Forward link channels
18
are structured to consist of traffic channels and overhead channels, including one or more paging channels. A paging channel
22
is used to communicate from the base station
14
to the mobile station
12
when the mobile station
12
is not assigned to a dedicated channel.
Code Division Multiple Access (CDMA) 2000 is a well known standard used in wireless communication systems. In CDMA2000, a quick paging channel (QPCH)
24
contains two-identical-bit messages that direct the mobile stations
12
to monitor their assigned slot on the paging channel
22
. Use of the QPCH
24
allows considerable improvements in standby time. In this circumstance, the mobile station
12
only needs to decode the two-identical-bit messages on the QPCH to determine if it needs to receive an incoming page. The QPCH
24
is a new feature in CDMA2000.
The QPCH reduces the amount of time a mobile station is awake. As used herein, a mobile station is awake when it is consuming power from a power source to demodulate a channel using a radio frequency receiver and demodulation hardware. As used herein, the term “wake up” is used to mean activation of, and application of a power source to, hardware necessary for demodulating a paging signal. Similarly the terms “sleep” and “go to sleep” refer to the deactivation of the hardware for the purpose of conserving a power source in the mobile station.
No error correction coding or interleaving is used for the QPCH paging indicator bits. Consequently, the time awake to receive the bits is small compared to the time awake to receive the regular paging channel slot. A pair of QPCH paging indicator bits indicate to the mobile station whether it is to wake up for its paging channel slot to receive a page. On-off keying is used by the base station to transmit the QPCH bits. For example, for one value the base station transmits a spread spectrum signal at a given power level during the bit time period using a particular spreading code and for the other value the base station does not transmit any power during the bit time period using the particular spreading code.
The paging channel
22
and the QPCH
24
are divided into slots. For example, the QPCH is divided into 80 ms slots called QPCH slots. The beginning of a QPCH slot occurs 100 ms earlier in time than the beginning of the associated PCH slot. Each QPCH slot is divided into four 20 ms frames. In a QPCH slot, a mobile station's first paging indicator bit will be in one of the first two 20 ms frames of the QPCH slot. A mobile station's second paging indicator bit will occur in the frame two frames after the frame containing the mobile station's first paging indicator bit. If the mobile station receives two paging indicator bits in a slot commanding the mobile station to wake up, the mobile station will wake up and monitor the paging channel
22
.
In conventional IS-95A/B systems, the standby time of the mobile station
12
is independent of the channel condition or the power allocation at the base station
14
. On the other hand, the base station
14
can adjust various parameters of the QPCH
24
that have an affect on the ability of the mobile station
12
to demodulate the QPCH
24
. For example, the transmission power
26
of the QPCH
24
can be adjusted at the base station
14
. CDMA2000 specifies that the QPCH's transmission power
26
relative to the pilot power range from 2 dB to −5 dB.
Also, the number of quick paging channels transmitted by the base station
14
also can be adjusted at the base station
14
. CDMA2000 specifies that one to three quick paging channels
24
can be allocated to each supported CDMA channel. The number of quick paging channels
30
influences the probability of a collision occurring. Collisions occur if the QPCH's indicator positions for two mobile stations
12
happen to be the same. In this case, if one of the mobile stations has a page, the base station
14
will send a signal to wake the mobile station
12
. Because two mobile stations have the same QPCH indicator positions, both mobile stations
12
will wake up. Additionally, the data rate
28
of the QPCH
24
can be adjusted at the base station
14
. CDMA
2000
specifies that the data rate
28
be 4800 bps or 9600 bps. With a higher data rate
28
, the base station can transmit more information, therefore there are more QPCH paging indicator positions.
However, there are trade-offs in adjusting the above parameters. Although using a higher data rate
28
reduces the chance of collision, it is well known that using a higher data rate with transmission power remaining the same results in worse performance in demodulation of the QPCH. This can cause an increased number of false page indications, thereby increasing the number of times the mobile station
12
is caused to wake up unnecessarily.
Additionally, one concern with respect to the base station
14
is the available power and transmission capacity of the base station. If more resources are allocated to the QPCH, there will be fewer resources allocated to the forward link traffic channel, which may result in the reduction of total system capacity. When the network load is high, i.e., when there are many active users or a high data rate request, it is likely that the service provider will prefer to provide service to the active users rather than increasing the standby time of the idle users. On the other hand, if the network load is low, the service provider has the ability to allocate more resources to the QPCH
24
while maintaining adequate services for the active users.
What is needed is a method of adaptively adjusting parameters of the QPCH
24
at the base station
14
according to current available network resources to maximize the standby time of the mobile stations
12
.
SUMMARY OF THE INVENTION
The invention satisfies the aforementioned needs by providing a method of adaptively allocating network resources to improve performance of a wireless communication device in a system in which a base station transmits a QPCH signal. The method includes identifying at least one parameter of the QPCH signal at the base station, monitoring the network load at the base station; and adaptively adjusting the at least one parameter at the base station based on the network load, such as the QPCH transmission power, to influence the performance of the wireless communication device.
REFERENCES:
patent: 5373506 (1994-12-01), Tayloe et al.
patent: 6307846 (2001-10-01), Willey
patent: WO 00/57662 (2000-09-01), None
Chen Jiangxin
Glazko Serguei
Riddle Christopher
Brown Charles D.
Cheatham Kevin T.
Gantt Alan T.
Maung Nay
Qualcomm Incorporated
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