Methods and apparatus related to composite beacon and wideband synchronization signaling
View Patent ↗A composite signal includes a high power beacon signal and low power corresponding wideband synchronization signal and is communicated over a time interval exceeding a single OFDM transmission time interval. A base station transmits one or more different such composite broadcast signals in a recurring timing structure. Each different potential beacon signal, e.g., a single tone signal, is paired with a unique wideband synchronization signal. A wideband synchronization signal includes at least some predetermined null tones and at least some predetermined non-null tones. For a given wideband synchronization signal, the predetermined null tones carry predetermined modulation symbol values, A wireless terminal receives a composite signal, identifies a beacon, determines a corresponding known wideband synchronization signal, compares received to known wideband synchronization signals, and determines at least one of a timing adjustment, frequency adjustment and channel estimation.
1. A method of operating a communication device to transmit composite signals, comprising:
transmitting a first composite signal including a first beacon signal and a first wideband synchronization signal, said first wideband synchronization signal including a first plurality of tones said first plurality of tones including at least some null tones and at least some low power tones, said low power tones having an average per tone power less than half the per tone power of any tones of said first beacon signal;
repeating said step of transmitting said first composite signal; and
transmitting a second composite signal including a second beacon signal which includes at least one tone which is not used to communicate said first beacon signal and a second wideband synchronization signal, said second wideband synchronization signal including a second plurality of tones said second plurality of tones including at least some null tones and at least some low power tones, said low power tones having an average per tone power less than half the per tone power of any tones of said second beacon signal, said transmitting of said second composite signal being performed during a time period which does not overlap transmission of said first composite signal.
2. The method of claim 1 wherein said second wideband synchronization signal includes non-null tones which are the same as the non-null tones of the first wideband synchronization signal but which communicate on at least one non-zero tone a modulation symbol which is different from the modulation symbol communicated on the at least one non-zero tone of the first wideband synchronization signal.
3. The method of claim 1 , wherein at least some non-null tones included in said second wideband synchronization signal are different than the non-null tones included in said first wideband synchronization signal.
4. The method of claim 1 , wherein said first and second wideband synchronization signals are unique and map to the first and the second beacon signals, respectively.
5. The method of claim 4 , further comprising transmitting a plurality of additional composite signals, each additional composite signal including an additional beacon signal and an additional wideband synchronization signal, each additional wideband synchronization signal including at least some null tones and at least some low power tones, said low power tones having an average per tone power less than half the per tone power of any tones of said additional beacon signals, each additional beacon signal corresponding to a different tone and each additional wideband synchronization signal being unique and corresponding to a single one of said additional beacon signals.
6. A communication device comprising:
a multi-tone transmitter for transmitting composite signals;
a control module for controlling said multi-tone transmitter to transmit a first composite signal including a first beacon signal and a first wideband synchronization signal, said first wideband synchronization signal including a first plurality of tones said first plurality of tones including at least some null tones and at least some low power tones, said low power tones having an average per tone power less than half the per tone power of any tones of said first beacon signal and to repeat said transmission of said first composite signal on a recurring basis;
stored transmission timing information indicating when said first composite signal and a second composite signal are to be transmitted;
stored signal definition information defining said first and second composite signals; and
wherein said control module further controls said multi-tone transmitter as a function of said stored transmission timing information and said stored signal definition information to transmit a second composite signal including a second beacon signal which includes at least one tone which is not used to communicate said first beacon signal and a second wideband synchronization signal, said second wideband synchronization signal including a second plurality of tones said second plurality of tones including at least some null tones and at least some low power tones, said low power tones having an average per tone power less than half the per tone power of any tones of said second beacon signal, said transmitting of said second composite signal being performed during a time period which does not overlap transmission of said first composite signal.
7. The communication device of claim 6 wherein said stored signal information indicates that said second wideband synchronization signal include non-null tones which are the same as the non-null tones of the first wideband synchronization signal but which communicate on at least one non-zero tone a modulation symbol which is different from the modulation symbol communicated on the at least one non-zero tone of the first wideband synchronization signal.
8. The communication device of claim 6 , wherein said stored signal information indicates that at least some non-null tones included in said second wideband synchronization signal are different than the non-null tones included in said first wideband synchronization signal.
9. The communication device of claim 6 , wherein said first and second wideband synchronization signals are unique and map to the first and the second beacon signals, respectively.
10. The communication device of claim 9 , further comprising:
additional stored transmission timing information indicating when a plurality of additional composite signals should be transmitted; and
additional stored signal definition information defining each of the plurality of additional composite signal to include an additional beacon signal and an additional wideband synchronization signal, each additional wideband synchronization signal including at least some null tones and at least some low power tones, said low power tones having an average per tone power less than half the per tone power of any tones of said additional beacon signals, each additional beacon signal corresponding to a different tone and each additional wideband synchronization signal being unique and corresponding to a single one of said additional beacon signals.
11. A communication device comprising:
means for transmitting multi-tone composite signals;
means for controlling said means for transmitting multi-tone composite signals to transmit a first composite signal including a first beacon signal and a first wideband synchronization signal, said first wideband synchronization signal including a first plurality of tones said first plurality of tones including at least some null tones and at least some low power tones, said low power tones having an average per tone power less than half the per tone power of any tones of said first beacon signal and to repeat said transmission of said first composite signal on a recurring basis;
means for storing transmission timing information indicating when said first composite signal and a second composite signal are to be transmitted;
means for storing signal definition information defining said first and second composite signals; and
wherein said control means further controls said multi-tone transmitter as a function of said stored transmission timing information and said stored signal definition information to transmit a second composite signal including a second beacon signal which includes at least one tone which is not used to communicate said first beacon signal and a second wideband synchronization signal, said second wideband synchronization signal including a second plurality of tones said second plurality of tones including at least some null tones and at least some low power tones, said low power tones having an average per tone power less than half the per tone power of any tones of said second beacon signal, said transmitting of said second composite signal being performed during a time period which does not overlap transmission of said first composite signal.
12. The communication device of claim 11 wherein said means for storing signal information stores information indicating that said second wideband synchronization signal include non-null tones which are the same as the non-null tones of the first wideband synchronization signal but which communicate on at least one non-zero tone a modulation symbol which is different from the modulation symbol communicated on the at least one non-zero tone of the first wideband synchronization signal.
13. The communication device of claim 11 , wherein said means for storing signal information stores information indicating that at least some non-null tones included in said second wideband synchronization signal are different than the non-null tones included in said first wideband synchronization signal.
14. A computer readable medium storing a computer program, wherein execution of the computer program is for:
transmitting a first composite signal including a first beacon signal and a first wideband synchronization signal, said first wideband synchronization signal including a first plurality of tones said first plurality of tones including at least some null tones and at least some low power tones, said low power tones having an average per tone power less than half the per tone power of any tones of said first beacon signal;
repeating said step of transmitting said first composite signal; and
transmitting a second composite signal including a second beacon signal which includes at least one tone which is not used to communicate said first beacon signal and a second wideband synchronization signal, said second wideband synchronization signal including a second plurality of tones said second plurality of tones including at least some null tones and at least some low power tones, said low power tones having an average per tone power less than half the per tone power of any tones of said first beacon signal, said transmitting of said second composite signal being performed during a time period which does not overlap transmission of said first composite signal.