Collision avoidance
First Claim
1. In a code-division-multiple-access (CDMA) system employing spread-spectrum modulation comprising a base station (BS) comprising a BS-spread-spectrum transmitter and a BS-spread-spectrum receiver, and a plurality of mobile stations, each mobile station (MS) comprising an MS-spread-spectrum transmitter and an MS-spread-spectrum receiver, a method comprising the steps of:
- transmitting from the MS-spread-spectrum transmitter of one of the mobile stations an access preamble signal signifying an attempt to access an intended one of a plurality of uplink transmission channels;
receiving the access preamble via the BS-spread-spectrum receiver, at the base station;
responsive to receipt of the access preamble signal, transmitting an acknowledgment signal corresponding to the access preamble signal from the BS-spread-spectrum transmitter of the base station;
receiving the acknowledgment signal at the MS-spread-spectrum receiver of the one mobile station;
transmitting from the MS-spread-spectrum transmitter of the one mobile station a spread-spectrum signal comprising at least one of data and control information, over the one intended uplink transmission channel, responsive to the receipt of the acknowledgment signal;
transmitting a predetermined sequence from the BS-spread-spectrum transmitter, over a downlink channel corresponding to the one intended uplink transmission channel; and
continuing the transmitting from the MS-spread-spectrum transmitter of the one mobile station over the one intended uplink transmission channel, only upon successful reception of the predetermined sequence over the downlink channel corresponding to the one intended uplink transmission channel at the MS-spread-spectrum receiver of the one mobile station.
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Accused Products
Abstract
A code-division-multiple-access (CDMA) system provides a collision avoidance mechanism for packet communications. When mobile stations attempt to establish links with a base station, the base station selects one mobile station to transmit data over an intended uplink channel. The base station transmits a predetermined sequence, during the first frame of the data transmission over the downlink control channel that corresponds to the intended uplink channel. If several mobile stations detect or mis-perceive successful access attempts, those stations begin data transmissions via respective desired uplink channels. At the same time, the mobile stations listen for the known sequence over the various corresponding downlink channels. Upon successful detection of the known sequence, one mobile station continues transmission of its data over the intended channel. However, any contending mobile station that does not detect the known sequence on the appropriate downlink channel immediately stops its data transmission.
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Citations
20 Claims
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1. In a code-division-multiple-access (CDMA) system employing spread-spectrum modulation comprising a base station (BS) comprising a BS-spread-spectrum transmitter and a BS-spread-spectrum receiver, and a plurality of mobile stations, each mobile station (MS) comprising an MS-spread-spectrum transmitter and an MS-spread-spectrum receiver, a method comprising the steps of:
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transmitting from the MS-spread-spectrum transmitter of one of the mobile stations an access preamble signal signifying an attempt to access an intended one of a plurality of uplink transmission channels;
receiving the access preamble via the BS-spread-spectrum receiver, at the base station;
responsive to receipt of the access preamble signal, transmitting an acknowledgment signal corresponding to the access preamble signal from the BS-spread-spectrum transmitter of the base station;
receiving the acknowledgment signal at the MS-spread-spectrum receiver of the one mobile station;
transmitting from the MS-spread-spectrum transmitter of the one mobile station a spread-spectrum signal comprising at least one of data and control information, over the one intended uplink transmission channel, responsive to the receipt of the acknowledgment signal;
transmitting a predetermined sequence from the BS-spread-spectrum transmitter, over a downlink channel corresponding to the one intended uplink transmission channel; and
continuing the transmitting from the MS-spread-spectrum transmitter of the one mobile station over the one intended uplink transmission channel, only upon successful reception of the predetermined sequence over the downlink channel corresponding to the one intended uplink transmission channel at the MS-spread-spectrum receiver of the one mobile station. - View Dependent Claims (2, 3)
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4. A method, of collision avoidance in a wireless digital multiple-access communication system, comprising the steps of:
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transmitting a preamble signal as part of an attempt to access an intended one of a plurality of wireless uplink transmission channels of the system from a wireless digital remote station;
receiving an acknowledgement signal at the wireless digital remote station from a base station of the system, and perceiving the received acknowledgement signal as an acknowledgement corresponding to the transmitted preamble signal;
transmitting from the wireless digital remote station a signal comprising at least one of data and control information, over the one intended uplink transmission channel, responsive to the received acknowledgement signal;
if a predetermined sequence is received at the wireless digital remote station over a downlink channel corresponding to the one intended uplink transmission channel within a specified time interval, then continuing the transmission from the wireless digital remote station over the one intended uplink transmission channel; and
if the predetermined sequence is not received at the wireless digital remote station over the downlink channel corresponding to the one intended uplink transmission channel within the specified time interval, then stopping the transmission over the one intended uplink transmission channel. - View Dependent Claims (5, 6, 7, 8, 9)
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10. A code-division-multiple-access (CDMA) wireless base station, comprising:
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a CDMA transmitter;
a CDMA receiver; and
a controller coupled to the CDMA receiver for responding to signals received via the CDMA receiver and coupled for controlling the CDMA transmitter, such that in operation the CDMA base station is for performing the following steps;
(a) receiving an access attempt signal from a remote station, the access attempt signal identifying an intended one of a plurality of uplink transmission channels serviced through the CDMA wireless base station;
(b) transmitting an access acknowledgement signal corresponding to the received access attempt signal;
(c) transmitting a start of message indicator sequence as data over a downlink channel corresponding to the intended uplink transmission channel; and
(d) after the start of message indicator, transmitting data or control information intended for the remote station over the downlink channel corresponding to the intended uplink transmission channel. - View Dependent Claims (11, 12, 13, 14)
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15. A code-division-multiple-access (CDMA) wireless remote station, comprising:
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a CDMA transmitter;
a CDMA receiver; and
a controller coupled to the CDMA receiver for responding to signals received via the CDMA receiver and coupled for controlling the CDMA transmitter, such that in operation the CDMA remote station is for performing the following steps;
1) transmitting an access signal signifying an attempt to access an intended one of a plurality of uplink transmission channels of a wireless CDMA communication system;
2) receiving a signal from a base station of the system, and perceiving the received signal from the base station as an acknowledgement corresponding to the access signal;
3) transmitting a signal comprising at least one of data or control information, over the one intended uplink transmission channel, responsive to the perceived acknowledgement;
4) if a predetermined sequence is received over a downlink channel corresponding to the one intended uplink transmission channel within a specified time interval, then continuing the transmission over the one intended uplink transmission channel; and
5) if the predetermined sequence is not received over the downlink channel corresponding to the one intended uplink transmission channel within the specified time interval, then stopping the transmission over the one intended uplink transmission channel. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification