Communication system, communication apparatus and communication method

• US 8,818,312 B2
• Filed: 09/13/2012
• Issued: 08/26/2014
• Est. Priority Date: 12/17/2002
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Fujii, Kunihide, Morita, Tadashi, Arisawa, Shigeru, Takayama, Yoshihisa
• Primary Examiner(s): Bhattacharya, Sam
• Application Number:
  US13/614,832
• Publication Number:
  US 20130005287A1
• Time in Patent Office: 712 Days
• Field of Search: 455/127.1, 455/192.2, 455/226.1, 455/227, 455/234.1, 455/343.5
• US Class Current: 455/227
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/77 for interrogation
• CPC Class Codes: H04W 74/0808 using carrier sensing, e.g. carrier sense multiple access [CSMA]
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method for a communication device includes determining whether a first radio frequency (RF) signal at a level of at least a first predetermined field threshold is detected. The method also includes generating a second RF signal at a level of at least a second predetermined field threshold greater than the first predetermined field threshold, when the communication device receives an instruction to generate the second RF signal and the determining determines that the first RF signal at the level of at least the first predetermined field threshold is not detected. The method further includes receiving a load modulated RF signal in response to the second RF signal.

Claims

1. A method for a communication device, comprising:

determining whether a first radio frequency (RF) signal at a level of at least a first predetermined field threshold is detected;

generating a second RF signal at a level of at least a second predetermined field threshold greater than the first predetermined field threshold, when the communication device receives an instruction to generate the second RF signal and the determining determines that the first RF signal at the level of at least the first predetermined field threshold is not detected; and

receiving a load modulated RF signal in response to the second RF signal.

2. The method according to claim 1, further comprising:

preventing a generation of the second RF signal, when the communication device receives the instruction to generate the second RF signal and the determining determines that the first RF signal at the level of at least the first predetermined field threshold is detected.

3. The method according to claim 1, wherein the determining determines whether the first RF signal at the level of at least the first predetermined field threshold was detected during a duration of

T_IDT+n×

T_RFW,

where

T_IDT>

4096/fc,

T_RFW=512/fc, and

0≦

n≦

3,

 

fc being a carrier frequency of the second RF signal, n being a randomly generated number.

4. The method according to claim 1, wherein a carrier frequency of the first RF signal is 13.56 MHz, and a carrier frequency of the second RF signal is 13.56 MHz.

5. A communication device, comprising:

circuitry configured to

determine whether a first radio frequency (RF) signal at a level of at least a first predetermined field threshold is detected;

generate a second RF signal at a level of at least a second predetermined field threshold greater than the first predetermined field threshold, when the communication device receives an instruction to generate the second RF signal and it is determined that the first RF signal at the level of at least the first predetermined field threshold is not detected; and

receive a load modulated RF signal in response to the second RF signal.

6. The communication device according to claim 5, wherein the circuitry is configured to prevent a generation of the second RF signal, when the communication device receives the instruction to generate the second RF signal and it is determined that the first RF signal at the level of at least the first predetermined field threshold is detected.

7. The communication device according to claim 5, wherein the circuitry is configured to determine whether the first RF signal at the level of at least the first predetermined field threshold was detected during a duration of

T_IDT+n×

T_RFW,

where

T_IDT>

4096/fc,

T_RFW=512/fc, and

0≦

n≦

3,

 

fc being a carrier frequency of the second RF signal, n being a randomly generated number.

8. The communication device according to claim 5, wherein a carrier frequency of the first RF signal is 13.56 MHz, and a carrier frequency of the second RF signal is 13.56 MHz.

9. A communication device, comprising:

means for determining whether a first radio frequency (RF) signal at a level of at least a first predetermined field threshold is detected;

means for generating a second RF signal at a level of at least a second predetermined field threshold greater than the first predetermined field threshold, when the communication device receives an instruction to generate the second RF signal and the means for determining determines that the first RF signal at the level of at least the first predetermined field threshold is not detected; and

means for receiving a load modulated RF signal in response to the second RF signal.

10. The communication device according to claim 9, wherein the means for determining prevents a generation of the second RF signal, when the communication device receives the instruction to generate the second RF signal and the means for determining determines that the first RF signal at the level of at least the first predetermined field threshold is detected.

11. The communication device according to claim 9, wherein the means for determining determines whether the first RF signal at the level of at least the first predetermined field threshold was detected during a duration of

T_IDT+n×

T_RFW,

where

T_IDT>

4096/fc,

T_RFW=512/fc, and

0≦

n≦

3,

 

fc being a carrier frequency of the second RF signal, n being a randomly generated number.

12. The communication device according to claim 9, wherein a carrier frequency of the first RF signal is 13.56 MHz, and a carrier frequency of the second RF signal is 13.56 MHz.