Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-10-26
2002-07-09
Jung, Min (Department: 2663)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
Reexamination Certificate
active
06418143
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates to data communications. More particularly, the present invention relates to a novel method and apparatus for extending the sequence numbering range applicable to selective repeat transmission protocols.
II. Description of the Related Art
FIG. 1
is a block diagram of a personal communication system configured in accordance with the use of the IS-95 over-the-air interface standard. The IS-95 standard, and its derivatives such as IS-95-A, IS-99, IS-707, IS-657 and ANSI J-STD-008 etc. (referred to herein collectively as the IS-95 standards), defines an interface for implementing a digital personal communication system using code division multiple access (CDMA) signal processing techniques. Also, a personal communication system configured substantially in accordance with the use of IS-95 is described in U.S. Pat. No. 5,103,459 entitled “System and Method for Generating Signal Waveforms in a CDMA Personal Communication System” assigned to the assignee of the present invention and incorporated herein by reference.
As is typical for most personal communication systems, IS-95 allows mobile telephone service to be provided to a set of wireless terminals (typically cellular telephones) using a set of base stations
12
coupled to the public switched telephone network (PSTN)
18
by a transmitter controller (BSC)
14
and a mobile switching center (MSC)
16
. During a telephone call, a wireless terminal
10
interfaces with one or more base stations
12
using CDMA modulated radio frequency (RF) signals. The RF signal transmitted from the base station
12
to the wireless terminal
10
is referred to as the forward link, and the RF signal transmitted from the wireless terminal
10
to the base station
12
is referred to as the reverse link.
Under the IS-99 and IS-707 standards (referred to hereinafter simply as IS-707), an IS-95 compliant communications system can also provide data communications services. Data communications services allow digital data to be exchanged using receiver
10
and the RF interface to one or more transmitters
12
. Examples of the type of digital data typically transmitted using the IS-707 standard include computer files and electronic mail.
In accordance with both the IS-95 and IS-707 standards, the data exchanged between a wireless terminal
10
and a base station
12
is processed in frames. To increase the likelihood that a frame will be successfully transmitted during a data transmission, IS-707 employs a radio link protocol (RLP) to track the frames transmitted successfully, and to perform frame retransmission when a frame is not transmitted successfully. Retransmission is performed up to three (3) times in IS-707, and it is the responsibility of the higher layer protocols to take additional steps to ensure the frame transmitted is successful.
In order to track which frames have been transmitted successfully, IS-707 calls for an eight-bit sequence number to be included in each frame transmitted. The sequence number is incremented for each frame from 0 to 256 and then reset back to zero. An unsuccessfully transmitted frame is detected when a frame with an out of order sequence number is received, or an error is detected using CRC checksum information or other error detection methods. Once an unsuccessfully transmitted frame is detected, the receive transmits a negative-acknowledgment message (NAK) to the transmit system that includes the sequence number of the frame that was not received. The transmit system then retransmits the frame including the sequence number as originally transmitted. If the retransmitted frame is not received successfully, a second negative-acknowledgment message is sent to the transmit system. The transmit system typically responds by notifying the controlling application or network layer of the failed transmission.
Under IS-95A and IS-707, frames are transmitted once every 20 milliseconds (ms). Thus, an eight-bit sequence number can track 256 frames transmitted over a five (5) second interval. Five seconds is typically sufficient to allow a failed frame transmission to be detected, and a retransmission to be performed, and therefore an eight-bit sequence number provides sufficient time for frame retransmission. Thus, retransmitted frames can be uniquely identified without ambiguity caused by a sequence “wrap-around” whereby the eight bit sequence number repeats.
Since the original development of IS-95A and IS-707, however, additional protocols and standards have been proposed and developed that allow data to be transmitted at greater rates. Typically, these new protocols and standards use the same frame structure as IS-95A and IS-707 in order to maintain as much compatibility as possible with pre-existing systems and standards. However, while maintaining compatibility with pre-existing standards and systems is desirable, the use of the same type of frame within these higher rate protocols and standards substantially increases the number of frames that are transmitted during a given period of time. For example, if the transmission rate is increased by a factor of four, the time required to transmit 256 frames is reduced to 1.25 seconds, rather than the five seconds required previously. A time period of 1.25 seconds is typically insufficient to allow a failed frame transmission to be detected, and a retransmission attempted, before the eight-bit sequence number repeats. Thus, the use of an eight-bit sequence number is insufficient to allow unique identification frames for the time period necessary to perform the desired retransmission sequence.
While the number of bits in the sequence number could be increased, such an increase would substantially alter the frame format and therefore violate the goal of maintaining substantial compatibility with previously existing systems and standards. Thus, the present invention is directed to a method and apparatus for extending the sequence number range without modifying the number of bits used for the sequence number.
SUMMARY OF THE INVENTION
The present invention is a novel and improved method and apparatus for extending the sequence numbering range for a selective repeat transmission protocol. In accordance with one embodiment of the invention, data frames are transmitted including an eight-bit sequence number and a one-bit retransmit flag. The one bit retransmit flag indicates whether the frame is newly transmitted or retransmitted due to a failed first transmission. The transmit and receive systems each maintain a twelve-bit sequence number referred to as a “long sequence number” comprised of the eight-bit sequence number transmitted with each frame and a four-bit extension. The long sequence number is transmitted within control frames and the eight-bit sequence number is transmitted within the data frames.
REFERENCES:
patent: 4439859 (1984-03-01), Donnan
patent: 4617657 (1986-10-01), Drynan et al.
patent: 5151899 (1992-09-01), Thomas et al.
patent: 5291483 (1994-03-01), Nagai et al.
patent: 5337313 (1994-08-01), Buchholz et al.
patent: 5784362 (1998-07-01), Turina
patent: 6011796 (2000-01-01), Rezaiifar et al.
TAI/EIA/IS-99 Interim Standard Data Services Option for Wideband Spread Spectrum Digital Cellular System, Jul. 1995.
Bender Paul E.
Rezaiifar Ramin
Tiedemann Jr. Edward G.
Tomcik James D.
Baker Kent D.
Beladi S. Hossain
Jung Min
QUALCOMM Incorporated
Wadsworth Philip
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