Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1998-02-27
2001-04-03
Olms, Douglas (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S216000, C370S241000, C370S332000, 37, C455S466000
Reexamination Certificate
active
06212203
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to wireless communications. In particular the present invention relates to the processing of messages received from wireless communication links.
BACKGROUND OF THE INVENTION
Public cellular networks (public land mobile networks) are commonly employed to provide voice and data communications to a plurality of subscribers. For example, analog cellular radiotelephone systems, such as designated AMPS, ETACS, NMT-450, and NMT-900, have been deployed successfully throughout the world. More recently, digital cellular radiotelephone systems such as designated IS-54B and IS-136 in North America and the pan-European GSM system have been introduced. Several systems for providing wireless voice and data communications are described, for example, in the book titled
Cellular Radio Systems
by Balston, et al., published by Artech House, Norwood, Mass., 1993. In addition, satellite based radio communication systems are also being utilized to provide wireless communications in various regions such as the Asian Cellular Satellite System (ACeS).
Typically, modern cellular systems use communication protocols which receive messages as frames which either singly or in combination contain a message. An example of one such communication protocol used in modern wireless communication systems is the IS-136 standard. IS-136 is the TDMA (Time Division Multiple Access) Digital Analog Mobile Phone System Cellular (D-AMPS) specification. One feature introduced with IS-136 is a layered protocol for the digital control channel. These three layers are illustrated in FIG.
1
and include the Physical Layer (L
1
), the Data Link Layer (L
2
) and the Call Processing Layer (L
3
).
The Physical Layer (L
1
) provides access to the wireless communication media which is a 4,860 bits/second &pgr;/4 Differential Quadrature Phase Shift Keying (DQPSK) channel. The Physical Layer includes a physical channel that is divided into 40 ms frames, each of which is sub-divided into 6 slots. Data is convolutionally encoded which allows for 125 bits of Layer
2
data per slot of the physical channel if the CRC, L
3
Data and L
2
header are included.
The Data Link Layer (L
2
) monitors and controls reverse accesses, decodes L
2
messages and buffers the resultant L
3
data, filters messages not destined for the mobile station and controls the mobile low power duration. L
2
resolves messages into either an Fast Broadcast Control Channel (FBCCH), an Extended Broadcast Control Channel (EBCCH), or a SMS,PCH and ARCH Channel (SPACH) message. FBCCH and EBCCH messages are broadcast messages which are intended for all mobile stations. SPACH messages are addressed to a specific mobile station, for example, incoming calls are SPACH messages. SPACH messages are further divided into Paging Channel (PCH) messages which are used for initially notifying a mobile station of an event, Short Message Service Channel (SMSCH) messages which are used for transmission of short messages, or Access Response Channel (ARCH) messages which are used for conveying responses to the mobile station after the mobile station has transmitted a message.
The Call Processing Layer (L
3
) is a state machine which defines the state of the mobile station. The mobile station waits for incoming notices by “camping” on a control channel. The mobile station leaves the camping state to handle an incoming PCH message, to handle an origination attempt, to register, or to send a short text message, etc.
As is briefly described above, an IS-136 system receives frames which are decoded by L
2
which also buffers the L
3
data of a message. Thus, L
2
assembles messages from the frames and passes the messages to L
3
. L
3
then carries out the operations specified by the messages received from L
2
. One difficulty with such a system may arise where fewer than all of the frames of a message are received by L
2
such that a complete message cannot be assembled and forwarded to L
3
(i.e., some L
3
data is lost). Currently, systems known to the inventors discard these incomplete messages either at L
2
or L
3
. Thus, the loss of a message, which may span multiple frames, may result from the loss of a single frame. In transmission environments where the loss of frames is common, this loss of messages typically reduces the efficiency of communication.
In light of the above discussion, a need exists for improvements in the processing of messages from frames received in a wireless communication system so as to reduce the likelihood that messages will be lost.
SUMMARY OF THE INVENTION
In view of the above discussion, it is an object of the present invention to provide improved processing of messages in a lost data circumstance.
Another object of the present invention is to reduce the number of discarded messages resulting from a loss or error condition associated with a frame.
Still another object of the present invention is to provide improved processing of messages transmitted in a lost data circumstance in a manner which is compatible with existing wireless communication protocols.
These and other objects of the present invention are provided by methods, systems and computer program products which improve message processing in lost data circumstances for a communication system communicating over a wireless communication link by receiving part of a message which has been transmitted over the wireless communication link and determining if sufficient information was received in the message to perform an operation specified by the message. The operation is performed if it is determined that sufficient information was received in the message to perform the specified operation.
By evaluating partially received messages, the present invention allows for the recovery of messages from transmissions which would otherwise have been discarded, thereby, reducing the number of discarded messages. Thus, the present invention improves the ability of a station to recover messages in lost data circumstances as long as enough of the message is received to perform at least one operation specified by the message.
In a further embodiment of the present invention, the communication system operates utilizing a layered communication protocol. In such a case, a first layer of the layered communication protocol receives frames of a message and provides, to a second layer of the layered communication protocol, a partial message if the entire message is not received by the first layer. Information about how much and what portions of the message are missing may also be supplied. The partial message received by the first layer is received by a second layer of the communication protocol which determines if sufficient information is included in the partial message to perform an operation specified by the message. The partial message may be provided to the second layer if an error in receiving a frame of the message occurs or upon occurrence of a timeout condition associated with the message.
In a particular embodiment, a partial message may be assembled from the frames received by the first layer if all of the frames of a message are not received by the first layer and the assembled partial message provided to the second layer.
Another embodiment of the present invention provides improved message processing in lost data circumstances for a radiotelephone communicating over a wireless communication link utilizing a communication protocol having messages which contain both mandatory elements and optional elements. In such an embodiment, frames of a message having both mandatory and optional elements are received from the wireless communication link. It is then determined if all of the frames associated with a message received from the wireless communication link are less than all of the frames specified for the message. A partial message corresponding to the frames received from the wireless communication link is then assembled if the frames received from the wireless communication link are less than all of the frames specified for the message. It is then determined
Anderson Keith William
Burdette Brian Alan
Ericsson Inc.
Hom Shick
Myers Bigel & Sibley & Sajovec
Olms Douglas
LandOfFree
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