Method and device for prompt and efficient service discovery in wireless networks

Abstract

Methods, system and apparatus are provided for advertising service offerings in a communication system. An example embodiment comprises at least one device. A first device broadcasts a message of a first type, chooses a value for a time limit and listens for a message sent by a second device. If no message has been received before time limit, elapse, it again broadcasts a message of a first type. Otherwise, the message received from said second device is analyzed and if said message includes valid information about said first device chooses a value for the time limit. However, if said message received does not include valid service description about said first device, a message of a second type is broadcast. This reduces useless broadcast of a complete service list. Broadcast may be initiated more often and, service discovery for new devices coming into proximity takes less time.

1. A method comprising advertising service offerings in a wireless communication system including at least one device wherein a first device performs the steps of:
 broadcasting a message of a first type,  
 choosing a value for a time limit,  
 listening and waiting for a message from a second device,  
 if no message has been received until elapse of said time limit, continuing with the step of broadcasting a message of a first type, otherwise  
 analyzing the message received from said second device and if message includes valid information about said first device, continuing with the step of choosing a value for a time limit, and  
 broadcasting a message of a second type, if said message received from said second device does not include valid service description about said first device,  
 wherein the first device maintains a counter for each service description, and further comprising the step of incrementing the counter for service descriptions broadcast with a message, and further comprising the step of analyzing counter values and deriving a value indicating a distance between the first device and any of the other known devices.  
 
     
     
       2. The method according to  claim 1 , wherein said message of the first type comprises a digest of a service description of the first device. 
     
     
       3. The method according to  claim 2 , wherein said message of the first type comprises a digest of service descriptions of other devices, the service descriptions being stored in said first device. 
     
     
       4. The method according to  claim 1 , wherein said message of the second type comprises the service description of the first device. 
     
     
       5. The method according to  claim 1 , wherein said message of the second type comprises the service descriptions of other devices, the service description of which are stored in said first device. 
     
     
       6. The method according to  claim 4 , wherein only a digest of the service description is sent for all devices, for which information received from the second device is valid. 
     
     
       7. The method according to  claim 1 , wherein the information received by the second device is formed by one of the service description, a service description digest. 
     
     
       8. The method according to  claim 1 , wherein the step of analyzing counter values includes the step of filtering out devices having a counter value higher than a predetermined threshold. 
     
     
       9. The method according to  claim 1 , wherein the step of marking a service to be too far away in response to a message indicating such service is too far away, whereby the message originates from a service considered not too far away. 
     
     
       10. The method according to  claim 1 , wherein messages of the first and second type include counter values related to the service descriptions. 
     
     
       11. A system for advertising service offerings in a communication system comprising at least one device, the device comprising means adapted to perform the method according to  claim 1 . 
     
     
       12. A computer program product stored on a computer usable medium, comprising computer readable program means for causing a computer to perform a method according to  claim 1 . 
     
     
       13. An article of manufacture comprising a computer usable medium having computer readable program code means embodied therein for causing advertisement of service offering in a wireless communication system including at least one device, the computer readable program code means in said article of manufacture comprising computer readable program code means for causing a computer to effect the steps of:
 a first device performs the steps of:  
 broadcasting a message of a first type,  
 choosing a value for a time limit,  
 listening and waiting for a message from a second device,  
 if no message has been received until elapse of said time limit, continuing with the step of broadcasting a message of a first type, otherwise  
 analyzing the message received from said second device and if message includes valid information about said first device, continuing with the step of choosing a value for a time limit, and  
 broadcasting a message of a second type, if said message received from said second device does not include valid service description about said first device,  
 wherein the first device maintains a counter for each service description, and further comprising the step of incrementing the counter for service descriptions broadcast with a message, and  
 further comprising the step of analyzing counter values and deriving a value indicating a distance between the first device and any of the other known devices.  
 
     
     
       14. A program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for advertising service offerings, said method steps comprising the steps of:
 a first device performs the steps of:  
 broadcasting a message of a first type,  
 choosing a value for a time limit,  
 listening and waiting for a message from a second device,  
 if no message has been received until elapse of said time limit, continuing with the step of broadcasting a message of a first type, otherwise  
 analyzing the message received from said second device and if said message includes valid information about said first device, continuing with the step of choosing a value for a time limit, and  
 broadcasting a message of a second type, if said message received from said second device does not include valid service description about said first device,  
 wherein the first device maintains a counter for each service description, and further comprising the step of incrementing the counter for service descriptions broadcast with a message, and  
 further comprising the step of analyzing counter values and deriving a value indicating a distance between the first device and any of the other known devices.  
 
     
     
       15. A method of discovering service information of a plurality of devices in a wireless communications system performed by a first device of said plurality of devices, the method comprising:
   providing a first time limit for transmitting messages;        broadcasting a first message of a first type after expiration of the first time limit;        receiving a corresponding message from a second device;        providing a second time limit for transmitting messages; and        transmitting a second message of the first or a second type by the first device after expiration of a second time limit,        wherein the second message is of the first type if the corresponding message includes valid information of the first device,        wherein the second message is of the second type if the corresponding message does not include valid information of the first device,        wherein the first, second, and corresponding message carry service descriptions and counters associated with the service descriptions.     
     
     
       16. The method of  claim 15 , wherein the first and the second time limits are the same if the corresponding message includes valid information about the first device. 
     
     
       17. The method of  claim 15 , wherein the second time limit is shorter than the first time limit if the corresponding message does not includes valid information about the first device. 
     
     
       18. The method of  claim 15 , wherein the message of the first type comprises a digest of service descriptions of the first device. 
     
     
       19. The method of  claim 15 , wherein the messages of the first type comprises a digest of service descriptions of other devices, the service descriptions being stored in the first device. 
     
     
       20. The method of  claim 15 , wherein the message of the second type comprises the service descriptions of the first device. 
     
     
       21. The method of  claim 15 , wherein the message of the second type comprises the service descriptions of other devices, the service description of which are stored in the first device. 
     
     
       22. The method of  claim 18 , wherein service descriptions of the first device are sent to the rest of the devices in the wireless communication environment if the corresponding message includes valid information about the first device. 
     
     
       23. The method of  claim 15 , wherein the information received by the second device is formed by at least one service description and at least a service description digest. 
     
     
       24. The method of  claim 15 , wherein the counter values related to the service descriptions are updated every time a message of the first type is broadcasted. 
     
     
       25. The method of  claim 24 , wherein the counter values are compared with a predetermined threshold. 
     
     
       26. The method of  claim 25 , wherein the counter values are analyzed to determine a distance between the first and the second device. 
     
     
       27. The method of  claim 26 , wherein the distance between the first and the second device determines the availability of a service. 
     
     
       28. A method of discovering service information of a plurality of devices in a wireless communications system performed by a first device of said plurality of devices, the method comprising:
   providing a first time limit for transmitting messages;        receiving a first message of a first type from a second device;        providing a second time limit for transmitting messages;        transmitting a corresponding message after expiration of the second time limit, and        receiving a second message of the first or a second type from the second device;        wherein the second message is of the first type if the corresponding message includes valid information of the second device,        wherein the second message is a message of the second type if the corresponding message does not include valid information of the second device, and        wherein the first, second, and corresponding message carry service descriptions and counters associated with the service descriptions.     
     
     
       29. The method of  claim 28 , wherein the first and the second time limits are the same if the corresponding message includes valid information about the first device. 
     
     
       30. The method of  claim 28 , wherein the second time limit is shorter than the first one if the corresponding message does not includes valid information about the first device. 
     
     
       31. The method of  claim 28 , wherein the message of the first type comprises a digest of service descriptions of the first device. 
     
     
       32. The method of  claim 28 , wherein the message of the first type comprises a digest of service descriptions of other devices, the service descriptions being stored in the first device. 
     
     
       33. The method of  claim 28 , wherein the message of the second type comprises the service descriptions of the first device. 
     
     
       34. The method of  claim 28 , wherein the message of the second type comprises the service descriptions of other devices, the service description of which are stored in the first device. 
     
     
       35. The method of  claim 34 , wherein service descriptions of the first device are sent to the rest of the devices in the wireless communication environment if the corresponding message includes valid information about the first device. 
     
     
       36. The method of  claim 28 , wherein the information received by the second device is formed by at least one service description and at least a service description digest. 
     
     
       37. The method of  claim 28 , wherein the counters values associated with service descriptions are updated every time a message of the first type is broadcasted. 
     
     
       38. The method of  claim 28 , wherein the counter values are compared with a predetermined threshold. 
     
     
       39. The method of  claim 28 , wherein the counter values are analyzed to determine a distance between the first and the second device. 
     
     
       40. The method of  claim 39 , wherein the distance between the first and the second device determines the availability of a service.