Collision avoidance

• US 6,507,601 B2
• Filed: 02/08/2001
• Issued: 01/14/2003
• Est. Priority Date: 02/09/2000
• Status: Expired due to Fees

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Golden Bridge Technology
• Inventors: Parsa, Kourosh, Kanterakis, Emmanuel
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US09/778,955
• Publication Number:
  US 20010055293A1
• Time in Patent Office: 705 Days
• Field of Search: 375/130, 375/141, 375/146, 375/147, 370/441, 370/433, 370/342, 370/335, 370/461, 370/445, 370/448, 455/450, 455/455
• US Class Current: 375/141
• CPC Class Codes: H04B 1/69 Spread spectrum techniques
• CPC Class Codes: H04L 1/004 by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00
• CPC Class Codes: H04W 52/325 Power control of control or pilot channels
• CPC Class Codes: H04W 52/362 Aspects of the step size
• CPC Class Codes: H04W 52/48 during retransmission after error or non-acknowledgment
• CPC Class Codes: H04W 74/0816 with collision avoidance
• CPC Class Codes: H04W 74/085 collision avoidance

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.

Claims

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.

2. A method as in claim 1, further comprising the steps of:

perceiving a signal received at the MS-spread-spectrum receiver of another mobile station as an acknowledgment of an attempt by said another mobile station to access another one of a plurality of uplink transmission channels;

transmitting from the MS-spread-spectrum transmitter of said another mobile station a spread-spectrum signal comprising at least one of data and control information, over said another intended uplink transmission channel, responsive to the perceived acknowledgment;

waiting for receipt of the predetermined sequence from the base station, at the MS-spread-spectrum receiver of said another mobile station, over a downlink channel corresponding to said another intended uplink transmission channel; and

stopping the transmitting from the MS-spread-spectrum transmitter of said another mobile station over said another intended uplink transmission channel, if the predetermined sequence is not received over the downlink channel corresponding to said another intended uplink transmission channel.

3. A method as in claim 1, wherein:

the step of transmitting an access preamble signal comprises the steps of transmitting a plurality of access preambles at sequentially increasing power levels,

each transmitted access preamble comprises a signature corresponding to the intended one of a plurality of uplink transmission channels; and

the step of receiving the access preamble signal comprises detecting a first one of the access preambles that is received at the BS-spread-spectrum receiver at an adequate power level.

4. A method, of collision avoidance in a wireless digital multiple-access communication system, comprising the steps of:

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.

5. A method as in claim 4, wherein:

each of the transmitting steps comprises transmitting a spread-spectrum signal from the wireless digital remote station; and

each of the receiving steps comprises receiving a spread-spectrum signal at the wireless digital remote station.

6. A method as in claim 5, wherein:

the digital multiple-access system comprises a code-division multiple access (CDMA) type system;

each transmitted spread-spectrum signal comprises a direct sequence encoded spread-spectrum signal; and

each received spread-spectrum signal comprises a direct sequence encoded spread-spectrum signal.

7. A method as in claim 4, wherein:

the step of transmitting a preamble signal comprises transmitting an access preamble containing a signature corresponding to the intended one uplink transmission channel; and

the step of receiving an acknowledgement signal and perceiving the received acknowledgement signal as an acknowledgement corresponding to the transmitted preamble signal comprises perceiving that the received acknowledgement signal contains a signature corresponding to the signature contained in the access preamble.

8. A method as in claim 7, wherein the step of transmitting the access preamble comprises transmitting the access preamble a plurality of times at sequentially increasing power levels.

9. A method as in claim 7, wherein:

the step of transmitting a preamble signal further comprises transmitting a collision detection preamble signal after receiving the acknowledgement signal;

the method further comprises receiving an acknowledgement corresponding to the collision detection preamble signal; and

the transmitting over the one intended uplink transmission channel is further responsive to receipt of the acknowledgement corresponding to the collision detection preamble signal.

10. A code-division-multiple-access (CDMA) wireless base station, comprising:

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) after the access acknowledgement, transmitting a start of message indicator sequence as data over a downlink channel corresponding to the intended uplink transmission channel, the start of message indicator sequence indicating to the remote station that the remote station can continue a data transmission over 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.

11. A CDMA base station as in claim 10, wherein the controller is further responsive to the CDMA receiver and controls the CDMA transmitter, such that in operation the CDMA base station performs a collision detection phase after transmitting the acknowledgement signal and before transmitting over the downlink channel corresponding to the intended uplink transmission channel.

12. A CDMA base station as in claim 10, wherein the data or control information transmitted by the CDMA base station over the downlink channel corresponding to the intended uplink transmission channel comprises closed loop power control information intended for the remote station.

13. A CDMA base station as in claim 10, wherein the CDMA receiver receives data or control information from the mobile station over the intended uplink channel substantially during and after the transmission of start of message indicator sequence.

14. A CDMA base station as in claim 13, wherein data or control information received from the mobile station over the intended uplink channel comprises data and closed loop power control information.

15. A code-division-multiple-access (CDMA) wireless remote station, comprising:

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.

16. A CDMA wireless remote station as in claim 15, wherein the controller is further responsive to the CDMA receiver and controls the CDMA transmitter, such that in operation the CDMA wireless remote station performs a collision detection phase after perceiving the acknowledgement and before transmitting the data or control information over the one intended uplink transmission channel.

17. A CDMA wireless remote station as in claim 15, wherein the controller is further responsive to the CDMA receiver such that in operation the CDMA wireless remote station receives data or control information over the downlink channel corresponding to the one intended uplink transmission channel following receipt of the predetermined sequence.

18. A CDMA wireless remote station as in claim 17, wherein the received data or control information comprises closed loop power control information intended for the remote station.

19. A CDMA wireless remote station as in claim 15, wherein the data or control information transmitted over the intended uplink channel comprises closed loop power control information and data.

20. A CDMA wireless remote station as in claim 15, wherein the controller further controls the CDMA transmitter, such that the transmitting of the access signal comprises repetitively transmitting an access preamble at sequentially increasing power levels, the access preamble comprising a signature corresponding to the one intended uplink transmission channel.