Digital radio communication

Abstract

A method of digital radio communication between a first device 2 and a second device 8, where each device comprises a radio transmitter 4, 10 and a radio receiver 6, 12, the method comprising: a) said first and second devices 2, 8 establishing a connection using a predetermined protocol having at least one predefined message format; b) if said connection is subsequently broken, said second device 8 transmitting an advertising message at a first data rate indicating a desire to reconnect; and c) if a reconnection is not established, said second device 8 transmitting a further advertising message at a second data rate indicating a desire to reconnect, wherein said second data rate is lower than the first data rate.

1 . A method of digital radio communication between a first device and a second device, each comprising a radio transmitter and a radio receiver, the method comprising:
 a) said first and second devices establishing a connection using a predetermined protocol having at least one predefined message format;   b) if said connection is subsequently broken, said second device transmitting an advertising message at a first data rate indicating a desire to reconnect; and   c) if a reconnection is not established, said second device transmitting a further advertising message at a second data rate indicating a desire to reconnect, wherein said second data rate is lower than the first data rate.   
     
     
         2 . A method as claimed in  claim 1  wherein the first device comprises a master device and the second device comprises a slave device. 
     
     
         3 . A method as claimed in  claim 1  wherein the lower data rate results from at least part of said further advertising message being encoded using a coding scheme in which at least some bits specified in said predefined message format are represented by a plurality of bits transmitted. 
     
     
         4 . A method as claimed  claim 3  wherein said coding scheme comprises a respective fixed sequence of chips to represent each data bit. 
     
     
         5 . A method as claimed in  claim 1  comprising the first and second devices agreeing during a connection that the second device will transmit said further advertising message if necessary to establish the reconnection. 
     
     
         6 . A method as claimed in  claim 1  comprising the second device transmitting a plurality of advertising messages at the first data rate. 
     
     
         7 . A method as claimed in  claim 1  further comprising said second device transmitting a further advertising message at the first data rate indicating a desire to reconnect. 
     
     
         8 . A method as claimed in  claim 1  comprising d) if a reconnection is not established at said second data rate, said second device transmitting a further advertising message at a third data rate indicating a desire to reconnect, wherein said third data rate is lower than the second data rate. 
     
     
         9 . A method as claimed in  claim 1  comprising said second device cycling through a plurality of available data rates for advertisement messages. 
     
     
         10 . A method as claimed in  claim 1  comprising the first device listening for messages at both said first and second data rates. 
     
     
         11 . A method as claimed in  claim 1  comprising the first and second devices conducting subsequent communication at a data rate applied to the advertisement message received by the second device in order to establish the reconnection. 
     
     
         12 . A method as claimed in  claim 11  comprising changing said data rate if a criterion is met. 
     
     
         13 . A method as claimed in  claim 12  wherein the criterion comprises a measure of a quality of signal between the first and second devices. 
     
     
         14 . A method as claimed in  claim 12  wherein said criterion comprises an estimate of the received signal strength from one of the devices to the other device. 
     
     
         15 . A method as claimed in  claim 11  comprising changing the data rate if the received signal strength of one device is determined to be above or below a threshold level. 
     
     
         16 . A method as claimed in  claim 1  wherein the predetermined protocol is compatible with a Bluetooth™ or Bluetooth Low Energy™ protocol. 
     
     
         17 . A method as claimed in  claim 16  wherein the advertising message and the further advertising message form part of one or more Advertising events in accordance with a Bluetooth™ protocol. 
     
     
         18 . A digital radio device comprising a radio transmitter and a radio receiver, the device being arranged:
 a) to establish a connection with another device using a predetermined protocol having at least one predefined message format;   b) if said connection is subsequently broken, to transmit an advertising message at a first data rate indicating a desire to reconnect; and   c) if a reconnection is not established, to transmit a further advertising message at a second data rate indicating a desire to reconnect, wherein said second data rate is lower than the first data rate.   
     
     
         19 . A device as claimed in  claim 18  wherein the lower data rate results from at least part of said further advertising message being encoded using a coding scheme in which at least some bits specified in said predefined message format are represented by a plurality of bits transmitted. 
     
     
         20 . A device as claimed  claim 19  wherein said coding scheme comprises a respective fixed sequence of chips to represent each data bit. 
     
     
         21 . A device as claimed in  claim 18  arranged to agree with the other device during a connection to transmit said further advertising message if necessary to establish the reconnection. 
     
     
         22 . A device as claimed in  claim 18  arranged to transmit a plurality of advertising messages at the first data rate. 
     
     
         23 . A device as claimed in  claim 18  arranged to transmit a further advertising message at the first data rate indicating a desire to reconnect. 
     
     
         24 . A device as claimed in  claim 18  arranged d) if a reconnection is not established at said second data rate, to transmit a further advertising message at a third data rate indicating a desire to reconnect, wherein said third data rate is lower than the second data rate. 
     
     
         25 . A device as claimed in  claim 18  arranged to cycle through a plurality of available data rates for advertisement messages. 
     
     
         26 . A device as claimed in  claim 18  arranged to conduct subsequent communication with the other device at a data rate applied to the advertisement message received by the device in order to establish the reconnection. 
     
     
         27 . A device as claimed in  claim 26  arranged to change said data rate if a criterion is met. 
     
     
         28 . A device as claimed in  claim 27  wherein the criterion comprises a measure of a quality of signal between from the other device. 
     
     
         29 . A method as claimed in  claim 27  wherein said criterion comprises an estimate of the received signal strength from the other device. 
     
     
         30 . A device as claimed in  claim 26  arranged to change the data rate if the received signal strength from the other device is determined to be above or below a threshold level. 
     
     
         31 . A device as claimed in  claim 18  wherein the predetermined protocol is compatible with a Bluetooth™ or Bluetooth Low Energy™ protocol. 
     
     
         32 . A device as claimed in  claim 31  wherein the advertising message and the further advertising message form part of one or more Advertising events in accordance with a Bluetooth™ specification. 
     
     
         33 . A digital radio communication system comprising a first device and a second device, each comprising a radio transmitter and a radio receiver, wherein:
 a) said first and second devices are arranged to establish a connection using a predetermined protocol having at least one predefined message format;   b) if said connection is subsequently broken, said second device is arranged to transmit an advertising message at a first data rate indicating a desire to reconnect; and   c) if a reconnection is not established, said second device is arranged to transmit a further advertising message at a second data rate indicating a desire to reconnect, wherein said second data rate is lower than the first data rate.   
     
     
         34 . A digital radio communication system as claimed in  claim 33  wherein one or both of said first and second devices comprise a device as claimed in  claim 18 .