Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-09-22
2002-04-02
Urban, Edward F. (Department: 2685)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S509000, C370S335000
Reexamination Certificate
active
06366779
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to digital wireless communication systems, and more particularly to methods for rapidly assigning traffic channels in digital wireless communications rapidly assigning traffic channels in digital wireless communications systems.
2. Description of Related Art
Wireless communication systems facilitate twoway communication between a plurality of subscriber mobile radio stations or “mobile stations” and a fixed network infrastructure. Typically, the mobile stations communicate with the fixed network infrastructure via a plurality of fixed base stations. Exemplary systems include such mobile cellular telephone systems as Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA) systems, and Frequency Division Multiple Access (FDMA) systems. The objective of these digital wireless communication systems is to provide communication channels on demand between the mobile stations and the base stations in order to connect the mobile station users with the fixed network infrastructure (usually a wired-line system).
Mobile stations typically communicate with base stations using a duplexing scheme that allows for the exchange of information in both directions of connection. In CDMA communication systems, transmissions from a base station to a mobile station are referred to as “forward link” transmissions. Transmissions from a mobile station to a base station are referred to as “reverse link” transmissions. The basic radio system parameters and call processing procedures for exemplary prior art CDMA systems is described by the TIA specification which is entitled “Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System,” TIA/EIA/IS-95-A, published in May 1995 by the Telecommunications Industry Association, and referred to hereafter as “IS-95”.
Both voice and data services are available using CDMA communication systems made in accordance with IS-95. However, disadvantageously, data calls use the same airlink protocols, traffic channels, physical layers, signaling methods, call processing schemes and airlink protocols are used by the voice calls. While the prior art call processing schemes and signaling methods are efficient and effective for voice services, they are inefficient for data services, especially when the data services comprise very short duration calls. As is described in more detail below, it can take between two and three seconds to establish or “setup” an average voice traffic channel using the prior art call processing schemes. While this setup time may be acceptable for a voice call that, on the average, may have a duration of between 100 and 300 seconds, it is unacceptable for a data call having a duration of only a few seconds, or less. Therefore, an improved technique is needed for assigning data traffic channels in a CDMA communication system. The causes of traffic channel assignment delays in the prior art systems become apparent by reviewing CDMA call flow examples. Therefore typical prior art CDMA call flow examples are now described.
CDMA Call Flow Examples
Table 1 shows a simple call flow example as set forth in IS95. Table 1 uses the following conventions:
All messages are received without error.
Receipt of messages is not shown (except in the handoff examples).
Acknowledgements are not shown.
Optional authentication procedures are not shown.
Optional private long code transitions are not shown.
TABLE 1
Simple Call Flow Example - Mobile Station Origination
Mobile Station
Base Station
Detects user-initiated call
Sends Origination Message
> Access Channel >
Sets up Traffic
Channel
Begins sending null
Traffic Channel data
Sets up Traffic Channel
< Paging Channel <
Sends Channel
Assignment
Message
Receives N
5m
consecutive
valid frames
Begins sending the Traffic
Acquires the
Channel preamble
Reverse Traffic
Channel
Begins transmitting null
< Forward Traffic <
Sends Base Station
Traffic Channel data
Channel
Acknowledgement
Order
Begins processing primary
< Forward Traffic <
Sends Service Option
traffic in accordance with
Channel
Response Order
Service Option 1
Optional
Optional
Sends Origination
> Reverse Traffic >
Continuation Message
Channel
Optional
Optional
Applies ring back in audio
< Forward Traffic <
Sends Alert With
path
Channel
Information Message
(ring back tone)
Optional
Optional
Removes ring back from
< Forward Traffic <
Sends Alert With
audio path
Channel
Information Message
(tones off)
(User conversation)
(User conversation)
Table 1 shows a simple call flow example wherein a mobile station originates a call. Base station originated calls follow similar procedures. Messages are transmitted from the mobile station to the base station using the access channel. Messages are transmitted from the base station to the mobile station using the paging channel. As shown in Table 1, the mobile station first detects a user-initiated call, and then sends an “origination” message via the CDMA access channel. The access channel is a slotted random access channel. The mobile station transmits on the access channel using a random access procedure. Many parameters of the random access procedure are supplied by the base station in an access parameters message. The entire process of transmitting one message and receiving (or failing to receive) an acknowledgement for that message is called an “access attempt.” Each transmission in the access attempt is called an “access probe.” Within an access attempt, access probes are grouped into access probe sequences. Each access probe sequence comprises a fixed number of access probes. The first access probe of each access probe sequence is transmitted at a specified power level relative to the nominal open loop power level. Each subsequent access probe is transmitted at a power level that is a specified amount higher than the previous access probe.
In normal CDMA operation, when a mobile station user initiates a phone call, the mobile station sends an access probe to the base station. If the access probe is properly received by the base station, the mobile station should receive back an acknowledgement from the base station. Once the acknowledgement is received by the mobile station, the mobile station is instructed by the base station to wait and to stop sending further access probes to the base station. This is necessary because access probes produce interference on the communication channel. The mobile station therefore waits until it is assigned a traffic channel by the base station. The base station then communicates this request for a traffic channel and information about the mobile station to a base station controller (BSC). The BSC performs several administrative functions, possibly including authenticating the mobile station . The BSC then reviews the pool of available resources and allocates an element for the requesting mobile station.
As shown in Table 1, the base station informs the mobile station of the traffic channel assignment by sending a channel assignment message via the paging channel. Once the mobile station receives its channel assignment from the base station, it changes its receive and transmit frequencies, in addition to other relevant parameters, to the assigned traffic channel. The mobile station then attempts to initiate communication on the assigned traffic channel by establishing or “setting up” the traffic channel. If the traffic channel initialization is successful, the mobile station then acquires the traffic channel. The mobile station then begins sending a preamble on the reverse traffic channel to allow the base station to acquire the mobile station. As shown in Table 1, the base station acquires the reverse traffic channel and sends a base station acknowledgement order to the mobile station if the reverse traffic channel was properly acquired. At this point the mobile station and the base station begin negotiating service. The communication link can fail at any point during this negotiation process. However, if the
Bender Paul E.
Grob Matthew S.
Karmi Gadi
Baker Kent D.
Beladi S. Hossain
Qualcomm Incorporated
Urban Edward F.
Wadsworth Philip
LandOfFree
Method and apparatus for rapid assignment of a traffic... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for rapid assignment of a traffic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for rapid assignment of a traffic... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2894868