Method for processing the random access transmission in the frequency domain

• US 8,391,131 B2
• Filed: 01/24/2007
• Issued: 03/05/2013
• Est. Priority Date: 02/03/2006
• Status: Active Grant

• Current Assignee: Unwired Planet LLC (JP Morgan Chase & Co)
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Baldemair, Robert, Haartsen, Jacobus Cornelis, Parkvall, Stefan, Peters, Gunnar, Sahlin, Henrik
• Primary Examiner(s): Shah, Chirag
• Assistant Examiner(s): Kang, Suk Jin
• Application Number:
  US12/162,522
• Publication Number:
  US 20090225707A1
• Time in Patent Office: 2,232 Days
• Field of Search: None
• US Class Current: 370/208
• CPC Class Codes: H04J 13/0003 Code application, i.e. aspects relating to how codes are applied to form multiplexed channels
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04W 74/08 Non-scheduled access, e.g. ALOHA hybrid access H04W74/02
• CPC Class Codes: H04W 74/0833 Random access procedures, e.g. with 4-step access

Abstract

There is provided a method of operating a communication system, the communication system comprising a user equipment and a receiver, the method in the system comprising generating a random access transmission in a user equipment and transmitting the random access transmission to the receiver in the communication system, the random access transmission including a preamble; receiving the random access transmission from the user equipment at the receiver; processing the random access transmission in the frequency domain to detect the preamble. In preferred embodiments of the invention, the preamble has a cyclic prefix, or is preceded by a plurality of zero-valued symbols.

Claims

1. A method of operating a device in a communication system including a receiver, the method comprising:

generating a random access transmission including a preamble followed by a plurality of zero-valued symbols, whereby a length of the zero-valued symbols corresponds to a sum of a maximum round-trip time for signals between the device and the receiver plus a maximum delay spread of a channel between the device and the receiver, the random access transmission being suitable for processing in a frequency domain by the receiver; and

transmitting the random access transmission to the receiver in the communication system,

wherein the preamble includes a first cyclic prefix,

further wherein the random access transmission comprises a message block, the message block including a second cyclic prefix, whereby the second cyclic prefix is shorter than the first cyclic prefix.

2. The method as claimed in claim 1, the random access transmission comprises a known training sequence in a trail of the preamble.

3. The method as claimed in claim 2, wherein at least a portion of the first cyclic prefix comprises a repeat of the known training sequence.

4. The method as claimed in claim 1, wherein, in the random access transmission, the preamble is preceded by a first plurality of zero-valued symbols.

5. The method as claimed in claim 1, whereby the second cyclic prefix has a length that is at least equal to the maximum delay spread of the channel between the device and the receiver.

6. The method as claimed in claim 1, whereby in the random access transmission, the message block ends with a known training sequence.

7. The method as claimed in claim 1, whereby a length of the second cyclic prefix is such that the second cyclic prefix preceding the message block corresponds to a known training sequence.

8. The method as claimed in claim 1, whereby the message block precedes the preamble.

9. The method as claimed in claim 8, whereby the message block is preceded by a second plurality of zero-valued symbols.

10. The method as claimed in claim 1, whereby the step of generating comprises generating a random access transmission in which the message block follows the preamble.

11. A method as claimed in claim 10, whereby the message block is followed by a third plurality of zero-valued symbols.

12. A device for use in a communication system including a receiver, the device comprising:

a transmitter for generating and transmitting a random access transmission towards the receiver in order to access the communication system, the random access transmission comprising a preamble followed by a plurality of zero-valued symbols, wherein a length of the zero-valued symbols correspond to a sum of a maximum round-trip time for signals between the device and the receiver plus a maximum delay spread of a channel between the device and the receiver, the random access transmission being suitable for processing in a frequency domain by the receiver in the communication system;

wherein the preamble includes a first cyclic prefix,

further wherein the random access transmission comprises a message block, the message block including a second cyclic prefix, whereby the second cyclic prefix is shorter than the first cyclic prefix.

13. The device as claimed in claim 12, wherein the transmitter generates the random access transmission such that the preamble is preceded by a first plurality of zero-valued symbols.

14. A method of operating a receiver in a communication system, the method comprising:

receiving, from a user equipment, a random access transmission being formed to allow processing in a frequency domain and including a preamble preceded by a first plurality of zero-valued symbols and/or followed by a second plurality of zero-valued symbols, whereby a length of the first plurality of zero-valued symbols corresponds to a maximum round-trip time for signals between the user equipment and the receiver plus a maximum delay spread of the channel between the user equipment and the receiver; and

processing the received random access transmission in the frequency domain by the steps of

applying a Fourier transform to a portion of the received random access transmission;

calculating a conjugate complex Fourier transform of each of a plurality of preambles in a set of possible preambles, and multiplying each of the calculated Fourier transformed preambles by a result of the applying step;

calculating an inverse Fourier transform of each result from the multiplying step; and

comparing results of the calculating of the inverse Fourier transform step with a threshold to determine which of the possible preambles was used in the random access transmission,

wherein the preamble includes a first cyclic prefix,

further wherein the random access transmission comprises a message block, the message block including a second cyclic prefix, whereby the second cyclic prefix is shorter than the first cyclic prefix.

15. The method as claimed in claim 14, further comprising the step of determining a received power level at the receiver from the determined preamble.

16. A receiver in a communication system comprising:

a processor for processing in a frequency domain, a random access transmission being formed to allow processing in the frequency domain and including a preamble preceded by a first plurality of zero-valued symbols and followed by a second plurality of zero-valued symbols, said processor adapted to

apply a Fourier transform to a portion of the received random access transmission;

calculate a conjugate complex Fourier transform of each of a plurality of preambles in a set of possible preambles, and multiplying each of the calculated Fourier transformed preambles by a result of the applying step;

calculate an inverse Fourier transform of each result from the multiplying step; and

compare results of the calculating of the inverse Fourier transform with a threshold to determine which of the possible preambles was used in the random access transmission,

wherein the preamble includes a first cyclic prefix,

further wherein the random access transmission comprises a message block, the message block including a second cyclic prefix, whereby the second cyclic prefix is shorter than the first cyclic prefix.