Method of resolving physical layer collisions in a random access protocol an a corresponding receiver

• US 6,636,494 B1
• Filed: 07/30/1999
• Issued: 10/21/2003
• Est. Priority Date: 07/02/1999
• Status: Expired due to Fees

• Current Assignee: Alcatel SA (Nokia Corporation)
• Original Assignee: Alcatel SA (Nokia Corporation)
• Inventors: Roux, Pierre
• Primary Examiner(s): Patel, Ajit
• Assistant Examiner(s): Shah, Chirag
• Application Number:
  US09/363,848
• Time in Patent Office: 1,544 Days
• Field of Search: 370/333, 370/335, 370/340, 370/342, 370/338, 370/349, 370/441, 370/447, 370/348, 375/148, 375/347, 375/267
• US Class Current: 370/333
• CPC Class Codes: H04B 1/7113 Determination of path profile
• CPC Class Codes: H04B 1/712 Weighting of fingers for combining, e.g. amplitude control or phase rotation using an inner loop
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/16 in which the return channel carries supervisory signals, e.g. repetition request signals
• CPC Class Codes: H04L 12/413 with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]
• CPC Class Codes: H04W 74/08 Non-scheduled access, e.g. ALOHA hybrid access H04W74/02

Abstract

The invention relates to a method of resolving collisions between at a receiver, and also to such a receiver. According to the invention, the method performed by the receiver processes the signal representative of a collision. The method consists in particular in selecting signal “fingers” having a power level greater than a threshold value, and in combining said fingers with one another to find configurations for which the packets that result from the combination are error-free, thereby enabling the transmitters from which the colliding packets originated to be identified.

Claims

1. A method of resolving collisions between packets transmitted to a receiver by different transmitters using a random access protocol, wherein a signal corresponding to at least two of said packets from different transmitters colliding is received at said receiver, the method comprising:

selecting fingers of said signal that have a power level greater than a threshold level;

searching for a first configuration of contributions from said fingers for which a resulting packet from said first configuration is error-free, and identifying a corresponding transmitter which transmitted the resulting packet from said first configuration; and

searching for a second configuration of contributions from said fingers for which a resulting packet from said second configuration is error-free, and identifying a corresponding transmitter which transmitted the resulting from said second configuration and is different from said transmitter which transmitted the resulting packet from said first configuration, said second configuration excluding contributions from said fingers of said first configuration.

2. A method according to claim 1, wherein said steps of searching for said first configuration and said second configuration each comprise determining whether said resulting packets are error-free by detecting errors based on a CRC check.

3. A method according to claim 1, further comprising transmitting an acknowledgement to each identified transmitter.

4. A method according to claim 1, wherein said step of searching for the first configuration comprises:

selecting a received signal finger having the highest power level; and

searching for a minimum configuration of contributions from fingers for which the resulting packet is error-free; and

wherein said second configuration excludes the fingers of said minimum configuration.

5. A method according to claim 1, wherein the method is used in a CDMA type cellular network during a stage in which connection messages are interchanged between a terminal and a base station, a collision occurring when said base station receives connection messages from at least two terminals using different preambles within a predetermined period of time.

6. A receiver for receiving packets transmitted by different transmitters using a random access protocol, said receiver comprising:

means for determining from a received signal fingers having a power level greater than a threshold value, said received signal corresponding to at least two said packets from said different transmitters colliding;

means for searching for a first configuration of contributions from said fingers for which a resulting packet from said first configuration is error-free and a second configuration of contributions from said fingers for which the resulting packet from said second configuration is error-free, wherein said second configuration excludes contributions from said fingers of said first configuration;

means for identifying a first transmitter which transmitted the resulting packet from said first configuration and a second transmitter which transmitted the resulting packet from said second configuration, wherein said second transmitter is different from said first transmitter.

7. A receiver according to claim 6, wherein said means for searching comprises:

means for combining contributions from said fingers; and

means for detecting the presence of errors in a packet.

8. A receiver according to claim 6, wherein said means for detecting the presence of errors comprises a CRC check for each of said resulting packets.

9. A receiver according to claim 6, wherein said receiver further comprises means for transmitting an acknowledgement to each of said identified transmitters.