Pilot signals for synchronization and/or channel estimation
View Patent ↗The frame words of the preferred embodiment are especially suitable for frame synchronization and/or channel estimation. By adding the autocorrelation and cross-correlation functions of frame words, double maximum values equal in magnitude and opposite polarity at zero and middle shifts are obtained. This property can be used to slot-by-slot, double-check frame synchronization timing, single frame synchronization and/or channel estimation and allows reduction of the synchronization search time. Further, the present invention allows a simpler construction of a correlator circuit for a receiver.
1. A method of confirming frame synchronization in a communication channel between a base station and a mobile station:
(a) generating control signals and data signals within the communication channel, said control signals having a first sequence of L-bits and a second sequence of L-bits;
(b) autocorrelating the first and second sequences to generate first and second autocorrelated values;
(c) cross-correlating the first and second sequences to generate fist and second cross-correlated values; and
(d) combining the first and second autocorrelated values and the first and second cross-correlated values.
2. The method of claim 1 , wherein lowest out-of-phase coefficients of the autocorrelation function is −4.
3. The method of claim 1 , wherein a result of step (d) comprise maximum peaks at zero and middle time shifts, which are equal to each other and opposite in polarity.
4. The method of claim 1 , wherein the communication channel includes a frame having L number of slots, wherein step (d) allows at least one of slot-by-slot frame synchronization, channel estimation, double check frame synchronization and single frame synchronization.
5. The method of claim 1 , wherein each of said first and second sequences of L-bits includes a first prescribed number (b 0 ) of bit values equal to “0 ” and a second prescribed number (b 1 ) of bit values equal to “1”, wherein b 1 −b 0 is +1 or −1.
6. The method of claim 1 , wherein the communication channel comprises a plurality of frames, each frame having L number of slots and each slot has N number of pilot bits such that there are N number of sequences of L-bits in a frame, said first and second sequences being sequences of the N number of sequences.
7. The method of claim 3 , wherein the maximum peak at zero time shift is a first prescribed number*L, and the maximum peak at middle time shift is —(prescribed number*L).
8. The method of claim 6 , wherein between adjacent sequences, there are a prescribed number b 3 of bit values which are the same and there a prescribed number b 4 of bit values which are different such that b 3 -b 4 is +1 or −1.
9. The method of claim 6 , wherein said control signals include a third sequence of L-bits and a fourth sequence of L-bits, and further comprising the steps of:
autocorrelating the third and fourth sequences to generate third and fourth autocorrelated values; and
cross-correlating the third and fourth sequences to generate third and fourth cross-correlated values, wherein the combining step comprises combining the first, second, third and fourth autocorrelated values and the first, second, third and fourth cross-correlated values.
10. The method of claim 9 , wherein the sequences used for frame synchronization are members of a family of i sequences.
11. The method of claim 10 , wherein i=8, L=15 and N=2 to 32, each frame having a period of 10 ms and each slot having a period of about 0.667 ms.
12. The method of claim 9 , wherein step (d) comprises adding the first, second, third and fourth autocorrelated values and adding the first, second, third and fourth cross-correlated values.
13. A method of confirming frame synchronization:
generating a plurality of frame words, each frame word having a plurality of bits;
performing autocorrelation functions on a pair of frame words to generate a pair of autocorrelated value sets;
performing cross-correlation function on a pair of frame words to generate a pair of cross-correlated value sets; and
combining the pair of autocorrelated value set and cross-correlated value sets such that two peak values equal in magnitude and opposite in polarity are achieved at zero and middle time shifts.
14. A method of generating pilot signals of a prescribed pattern within a frame having 15 slots:
generating N pilot bits for each slot; and
forming N words of 15-bit based on above generating step, wherein each of a prescribed number of N words has a first prescribed number b 0 of bit values of “0 ” and a second prescribed number b 1 of bit values of “1 ”, such that b 1 -b 0 is +1 or −1.