Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1997-05-02
2001-07-10
Nguyen, Chau (Department: 2663)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S520000
Reexamination Certificate
active
06259709
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to Time Division Multiple (TDM), or Time Division Duplex (TDD), communication systems which utilize the CT2 standard (European Telecommunication Standard I-ETS, “Radio Equipment and System (RES); Common air interface specification to be used for the interworking between cordless telephone apparatus in the frequency band 864, 1 MHz, including public access service,” November 1994) in particular. More particularly, this invention relates to a way of modifying a CT2 system to include “training” bits in the field normally reserved for the signaling channel of a TDM transmission or mux.
2. Discussion of Related Technology
The use of training bits is well known in the wireless communications art as a way to bring several aspects of a receiver to a steady state so information bits can be received correctly. In a TDM system, a gap of time typically occurs between one transmission burst and the next. For several reasons, a receiver may not be able to recall the exact parameters it used to receive the previous transmission burst, or, some parameters may have changed in the interim. For example, one parameter used is the slicing voltage level, i.e., that voltage above which is interpreted as a logic “1”and below which it is interpreted as a logic “0”. It is common to turn power to the receiver off when it is not receiving and restore power when it is time to receive again. Although, this power management scheme reduces power consumption, it produces transients that disturb the receiver parameters. A receiver typically uses the first few bits, commonly known as “training” bits, to re-acquire these parameters to enable correct reception of the information bits.
Multiplex 2, Multiplex 1.2 and Multiplex 1.4 implemented by the CT2 standard, commonly referred to as MUX 2, MUX 1.2 and MUX 1.4 respectively, do not include the use of training bits. When the receiver is turned back on after the off power gap time, the first 16 bits (MUX 2), or the first bit (MUX 1.2), or the first two bits (MUX 1.4) convey the signaling channel and must be received correctly to avoid disrupting the communication channel. This adds difficulty to designing a TDD system based on the CT2 standard and can add undue cost to the radio demodulator design, since the signaling channel is used by a base station and handset, for example, to ascertain the status of the communication link and in communication exchange. If the signaling channel cannot be received due to errors, then this forces a link re-establishment to occur. If errors persist, the link is never established.
SUMMARY OF THE INVENTION
The present invention implements a scheme which not only allows a wireless communications receiver to stabilize between one transmission burst and the next so that no data is lost, but it also repositions the signaling channel to the end of the burst where conditions are fairly stable and therefore, errors in the signaling channel are minimal. The three commonly used MUXes of a CT2 wireless communication system, namely MUX 1.2, MUX 1.4 and MUX 2, are typically preceded by a signaling channel consisting of D channel bits. The present invention determines when these D bits are received for each of their respective MUXes and prevents a wireless receiver from receiving the bits as D bits, and prevents a wireless transmitter from transmitting them as D bits. During the time when the D bits would normally be in the signaling channel field of the MUX message, “training” bits are instead inserted. The training bits are typically an alternating pattern of bits, such as a 1010 or 0101 pattern and are usually referred to by those in the art as a “preamble field.” The D bit suffix on the respective MUXes is not affected by the present invention and remains a part of the MUX message.
It is an object of the present invention to modify wireless communications CT2 circuitry so training bits are included in the serial data stream to ensure reliable reception of the signaling channel. The advantage is to simplify the design of the radio receiver to reduce its cost and to increase the assurance of acquisition of the transmission parameters for the receiver.
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Covell James J.
Magana Javier V.
Schnizlein Paul G.
Lee Chiho Andrew
Legerity Inc.
Nguyen Chau
Skjerven Morrill & MacPherson LLP
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