Method and arrangement in a telecommunication system

• US 9,179,478 B2
• Filed: 02/12/2013
• Issued: 11/03/2015
• Est. Priority Date: 02/03/2006
• Status: Active Grant

• Current Assignee: Unwired Planet LLC (JP Morgan Chase & Co)
• Original Assignee: Unwired Planet LLC (JP Morgan Chase & Co)
• 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:
  US13/765,237
• Publication Number:
  US 20140105124A1
• Time in Patent Office: 994 Days
• Field of Search: None
• US Class Current: 1/1
• 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, the method comprising:

generating a random access transmission including a preamble followed by a message block followed by a guard period, wherein;

the preamble includes a first cyclic prefix;

the message block includes a second cyclic prefix that is shorter than the first cyclic prefix, the second cyclic prefix having a length that is at least equal to a maximum delay spread of a channel between the device and a receiver in the communication system; and

a length of the guard period is at least a maximum round-trip time for signals between the device and the receiver; and

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

2. The method as claimed in claim 1, wherein the step of generating comprises generating a random access transmission in which the message block ends with a known training sequence.

3. The method as claimed in claim 1, wherein the step of generating comprises generating a random access transmission in which a trail of the preamble comprises a known training sequence.

4. The method as claimed in claim 3, wherein the step of generating comprises generating a random access transmission in which at least a portion of the first cyclic prefix comprises a repeat of the known training sequence.

5. The method as claimed in claim 3, wherein the step of generating comprises generating a random access transmission in which the message block ends with the known training sequence.

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

7. A device for use in a communication system, the device comprising:

a transmitter configured to generate and transmit a random access transmission to a receiver in order to access the communication system, the random access transmission comprising a preamble followed by a message block followed by a guard period, wherein;

the preamble includes a first cyclic prefix;

the message block includes a second cyclic prefix that is shorter than the first cyclic prefix, the second cyclic prefix having a length that is at least equal to a maximum delay spread of a channel between the device and the receiver; and

a length of the guard period is at least a maximum round-trip time for signals between the device and the receiver.

8. The device as claimed in claim 7, wherein the step of generating comprises generating a random access transmission in which the message block ends with a known training sequence.

9. The device as claimed in claim 7, wherein the step of generating comprises generating a random access transmission in which a trail of the preamble comprises a known training sequence.

10. The device as claimed in claim 9, wherein the step of generating comprises generating a random access transmission in which at least a portion of the first cyclic prefix comprises a repeat of the known training sequence.

11. The device as claimed in claim 9, wherein the step of generating comprises generating a random access transmission in which the message block ends with the known training sequence.

12. The device as claimed in claim 7, wherein the length of the second cyclic prefix is such that the second cyclic prefix preceding the message block corresponds to the known training sequence.

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

receiving from a user equipment a random access transmission including a preamble followed by a message block followed by a guard period, wherein;

the preamble includes a first cyclic prefix;

the message block includes a second cyclic prefix that is shorter than the first cyclic prefix, the second cyclic prefix having a length that is at least equal to a maximum delay spread of a channel between the user equipment and the receiver; and

a length of the guard period is at least a maximum round-trip time for signals between the user equipment and the receiver;

processing the 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 the result of the applying step;

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

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

decoding the message block after timing synchronisation has been established using the preamble.

14. The method as claimed in claim 13, further comprising the step of determining a received power level at the receiver from the detected preamble.

15. A receiver in a communication system comprising:

a processor; and

a memory coupled to the processor;

wherein the processor is configured to process in the frequency domain a random access transmission received from a user equipment, the random access transmission including a preamble followed by a message block followed by a guard period, wherein;

the preamble includes a first cyclic prefix;

the message block includes a second cyclic prefix that is shorter than the first cyclic prefix, the second cyclic prefix having a length that is at least equal to a maximum delay spread of a channel between the user equipment and the receiver; and

a length of the guard period is at least a maximum round-trip time for signals between the user equipment and the receiver;

said processor being configured 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 the result of the applying step;

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

compare the results of the calculating an inverse Fourier transform step with a threshold to determine which of the preambles was used in the random access transmission; and

decode the message block after timing synchronisation has been established using the preamble.

16. The receiver as claimed in claim 15, the process being configured to determine a received power level at the receiver from the preamble.