Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
1998-04-20
2001-11-27
Vo, Don N. (Department: 2631)
Pulse or digital communications
Spread spectrum
Direct sequence
C375S367000
Reexamination Certificate
active
06324208
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates in general to telecommunications systems and more particularly to an apparatus and method of establishing and maintaining communication paths in a wireless telecommunications system.
BACKGROUND OF THE INVENTION
Wireless telecommunications systems require transmitters and receivers in order to send and receive information over radio frequency signals in a network configuration. These transmitters and receivers may suffer from interference with other transmitters and receivers in and out of the network configuration. Such interference may be caused by each transmitter operating at a different transmitting power level. Control of the transmitting power of the transmitters has only been performed at each transmitter and not from a centralized location. Further, the transmitting power of a transmitter within a wireless telecommunication system has proved to be difficult to control with respect to the transmitting powers of other transmitters in the system. Therefore, it is desirable to obtain improved control of the transmitting power of each transmitter within a wireless telecommunications system.
Also, wireless telecommunications systems require radio links be established between corresponding transmitters and receivers in order to provide wireless communication transmissions. Interference and delays occur in achieving acquisition and establishment of each radio link. It becomes inefficient to acquire and establish a radio link every time a call is to be initiated. Problems with interference also occur if a radio link is maintained whether or not a call is in progress due to power needed to maintain the radio link. Therefore, it is desirable to avoid establishing a radio link for each call and avoid requires a greater amount of circuitry and software support to identify information from a corresponding transmitter operating at a different phase. Additionally, a phase difference between a receiver and transmitter may also be affected by changes in a path delay between the transmitter and the receiver. Therefore, it is desirable to be able to control the phase of transmitters and receivers in a wireless telecommunications system to provide improved radio frequency signal transmission.
Transmitters of the originating or destination sources may send information at one phase and the receivers of the destination or originating sources may receive information out of phase. In such a situation, the receivers will not know know at what portion in the data stream the receive process has started. Information is partitioned into frames and to adequately process the information the beginning of each frame should be identified. Conventional techniques to frame align information are cumbersome, slow in frame identification, and may lose frames of information. Therefore, it is desirable to quickly and easily identify the beginning of each frame of information to achieve proper processing.
WO-A-93/14588 describes a CDMA cellular communication system in which to permit maximum flexibility within a predefined structure, the communication of signals from the mobile station may be characterised in the form of an access channel or a traffic channel communication, in which various combinations of user traffic and/or signalling traffic may be transmitted.
U.S. Pat. No. 5,161,168 discloses a technique for wireless telephone communications between a central terminal and a plurality of subscriber terminals, in which a number of signals associated with the subscriber terminals are spread, the spread signals are combined, and then the combined signal is transmitted.
U.S. Pat. No. 5,103,459 discloses a spread-spectrum telecommunications system whereby the mobile units are synchronised using phase offset information contained in a pilot signal.
U.S. Pat. No. 5,383,219 discloses a CDMA telecommunications system in which a power control bit is multiplexed in place of another bit in the transmission frame prior to transmission of that frame to a mobile unit, the mobile unit then using the power control bit in order to determine whether to increment or decrement its output power level by a predetermined amount.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a method of controlling transmitting power in a subscriber terminal of a wireless telecommunications systems is provided which substantially eliminates or reduces disadvantages and problems associated with conventional wireless systems.
Viewed from one aspect, the present invention provides a subscriber terminal for communicating with a central terminal located at a fixed distance from the subscriber terminal, the subscriber terminal comprising: a spreader operable to receive an information signal, the spreader further operable to combine the information signal with a code sequence signal to generate a spread signal for transmission as an uplink signal to the central terminal; a receiver operable to receive a power control signal contained within an overhead channel inserted in to a downlink signal transmitted from the central terminal using a wireless link, the power control signal having a value determined as a result of comparing within the central terminal the power of the uplink signal with a desired threshold range; and a transmitter coupled to the spreader and operable to receive the spread signal, the transmitter operable to amplify the spread signal in response to the power control signal, the power control signal specifying a power adjustment to the spread signal.
According to an embodiment of the present invention, a method of controlling transmitting power in a subscriber terminal of a wireless telecommunications system that includes establishing a downlink communication path from a transmitter of a central terminal to a receiver of the subscriber terminal. A downlink signal is transmitted from the transmitter of the central terminal and received at the receiver of the subscriber terminal. The downlink signal includes a power control signal that is used to adjust a transmitting power of the transmitter in the subscriber terminal in order to establish an uplink communication path between the transmitter of the subscriber terminal and a receiver at the central terminal.
One technical advantage of this aspect of the present invention is to externally control the transmitting power of the transmitter in the subscriber terminal. Another. technical advantage is to control transmitting power through an overhead channel in the downlink signal from the central terminal to the subscriber terminal. Yet another technical advantage is to provide increasing and decreasing incremental adjustments to the transmitting power of the transmitter in the subscriber terminal. Still another technical advantage is to adjust the transmitting power to match the transmitting power of other subscriber terminals serviced by the central terminal.
In accordance with another aspect of the present invention, there is provided an apparatus and method of synchronizing a transmitter in a subscriber terminal of a wireless telecommunications system that substantially eliminates or reduces disadvantages and problems associated with conventional wireless communication techniques.
Viewed from another aspect, the present invention provide. a subscriber terminal for communicating with a central terminal located at a fixed distance from the subscriber terminal, the subscriber terminal comprising: a receiver operable to establish a downlink communication path from the central terminal to the subscriber terminal; a transmitter for transmitting an uplink signal to the central terminal; a spreader operable to receive an information signal, the spreader further operable to combine the information signal with a code sequence signal to generate a spread signal for transmission; the receiver being operable to receive a code synchronization signal from the central terminal using a wireless link, the code synchronization signal having a value determined as a result of comparing within the central terminal t
Bhagalia Shashikant
Cheung Yeung Joemanne Chi
Cooper Ian L.
Lysejko Martin
Airspan Networks Inc.
Baker & Botts L.L.P.
Vo Don N.
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