Method for Optimizing the Beam Directions and Periodicity of Synchronization Signal Block (SSB) Transmission
A method for optimizing Synchronization Signal Block (SSB) sweep by a gNodeB in a 5G wireless system includes: sweeping, by a gNB, SSBs and collecting a user equipment (UE)-specific beam direction history; determining, by at least one of an artificial intelligence (AI) and machine learning (ML) engine, an optimal number of SSB beams and optimal set of beam directions based on the UE-specific beam direction history, and a complementary set of beam directions for the optimal set of beam directions; transmitting, by the at least one of the AI and ML engine, both the optimal set and the complementary set of SSB beam directions to the gNB; and transmitting, by the gNB, i) at every t 1 milliseconds (ms), SSBs in the optimal beam directions, and ii) at every t 2 ms, SSBs in the optimal directions as well as the complementary directions, wherein t 2 >t 1 and t 1 , t 2 ∈{5, 10, 20, 40, 80, 160} ms.
1 . A method for optimizing Synchronization Signal Block (SSB) sweep by a gNodeB in a 5G wireless system, the method comprising the steps of:
sweeping, by a gNB, SSBs and collecting a user equipment (UE)-specific beam direction history;
determining, by at least one of an artificial intelligence (AI) and machine learning (ML) engine, an optimal number of SSB beams and optimal set of beam directions based on at least the UE-specific beam direction history, and a complementary set of beam directions for the optimal set of beam directions;
transmitting, by the at least one of the AI and ML engine, both the optimal set of beam directions and the complementary set of beam directions to the gNB; and
transmitting, by the gNB, i) at every t 1 milliseconds (ms), SSBs in the optimal beam directions, and ii) at every t 2 ms, SSBs in the optimal set of beam directions as well as the complementary set of beam directions, wherein t 2 >t 1 and t 1 , t 2 ∈{5, 10, 20, 40, 80, 160} ms.
2 . The method according to claim 1 , wherein the determining step comprises performing K-means Clustering per gNB basis.
3 . The method according to claim 2 , further comprising:
periodically updating, by the at least one of the AI and ML engine, SSB configurations comprising beam directions and periodicity, based on weighted average of latest data and previous data.
4 . The method according to claim 2 , wherein the determining the optimal number of SSB beams comprises a plurality of iterations of the following steps:
i) in each iteration, increasing nSSB representing the number of SSB beams by 1;
ii) performing the K-means Clustering with beam directions from the UE-specific beam directions history by setting the maximum number of clusters to nSSB;
iii) storing the result of the K-means Clustering including the azimuth direction and the elevation direction of the SSB beams; and
iv) computing beamCov representing beam gain achieved from the SSB beams at the individual directions of the UE-specific beam directions history.
5 . The method according to claim 4 , wherein the iterations of the steps for determining the optimal number of SSB beams are repeated until one of i) the beamCov is greater than or equal to the beamCovTh representing a specified minimum SSB beam gain to be achieve in a desired angular range for all the directions in the UE-specific beam directions history, or ii) the number of SSB beams reaches a specified maximum limit.
6 . The method according to claim 4 , wherein the periodicity of t 1 milliseconds for transmitting the SSBs in the optimal beam directions is determined from at least one of previously obtained doppler-spread and coherence-time history.
7 . The method according to claim 6 , wherein the periodicity of t 1 milliseconds for transmitting the SSBs in the optimal set of beam directions is determined as follows:
i) selecting values from the periodicity set of {5,10, 20, 40, 80, 160} ms that exceed the mean coherence-time of the coherence-time history; and
ii) specifying the smallest value among the selected values exceeding the mean coherence-time as the periodicity of t 1 milliseconds for transmitting the SSBs in the optimal set of beam directions.
8 . The method according to claim 6 , wherein the periodicity of t 2 milliseconds for transmitting the SSBs in the optimal set of beam directions as well as in the complementary set of beam directions is determined from the at least one of the previously obtained doppler-spread and coherence-time history, and wherein the periodicity of t 2 milliseconds for transmitting the SSBs in the optimal set of beam directions as well as in the complementary set of beam directions is determined as follows:
i) selecting values from the periodicity set of {5,10, 20, 40, 80, 160} ms that exceed the mean coherence-time of the coherence-time history; and
ii) specifying the largest value among the selected values exceeding the mean coherence-time as the periodicity of t 2 milliseconds for transmitting the SSBs in the optimal set of beam directions as well as in the complementary set of beam directions.
9 . The method according to claim 6 , wherein the periodicity of t 1 milliseconds for transmitting the SSBs in the optimal set of beam directions and the periodicity of t 2 milliseconds for transmitting the SSBs in the optimal set of beam directions as well as in the complementary set of beam directions are determined as follows:
i) selecting values from the periodicity set of {5,10, 20, 40, 80, 160} ms that exceed the mean coherence-time of the coherence-time history;
ii) specifying the smallest value among the selected values exceeding the mean coherence-time as the periodicity of t 1 milliseconds for transmitting the SSBs in the optimal set of beam directions; and
iii) specifying the largest value among the selected values exceeding the mean coherence-time as the periodicity of t 2 milliseconds for transmitting the SSBs in the optimal set of beam directions as well as in the complementary set of beam directions.
10 . The method according to claim 3 , wherein the determining the optimal number of SSB beams comprises a plurality of iterations of the following steps:
i) in each iteration, increasing nSSB representing the number of SSB beams by 1;
ii) performing the K-means Clustering with beam directions from the UE-specific beam directions history by setting the maximum number of clusters to nSSB;
iii) storing the result of the K-means Clustering including the azimuth direction and the elevation direction of the SSB beams; and
iv) computing beamCov representing beam gain achieved from the SSB beams at the individual directions of the UE-specific beam directions history.
11 . The method according to claim 10 , wherein the iterations of the steps for determining the optimal number of SSB beams are repeated until one of i) the beamCov is greater than or equal to the beamCovTh representing a specified minimum SSB beam gain to be achieve in a desired angular range for all the directions in the UE-specific beam directions history, or ii) the number of SSB beams reaches a specified maximum limit.
12 . The method according to claim 10 , wherein the periodicity of t 1 milliseconds for transmitting the SSBs in the optimal beam directions is determined from at least one of previously obtained doppler-spread and coherence-time history.
13 . The method according to claim 12 , wherein the periodicity of t 1 milliseconds for transmitting the SSBs in the optimal set of beam directions is determined as follows:
i) selecting values from the periodicity set of {5,10, 20, 40, 80, 160} ms that exceed the mean coherence-time of the coherence-time history; and
ii) specifying the smallest value among the selected values exceeding the mean coherence-time as the periodicity of t 1 milliseconds for transmitting the SSBs in the optimal set of beam directions.
14 . The method according to claim 12 , wherein the periodicity of t 2 milliseconds for transmitting the SSBs in the optimal set of beam directions as well as in the complementary set of beam directions is determined from the at least one of the previously obtained doppler-spread and coherence-time history, and wherein the periodicity of t 2 milliseconds for transmitting the SSBs in the optimal set of beam directions as well as in the complementary set of beam directions is determined as follows:
i) selecting values from the periodicity set of {5,10, 20, 40, 80, 160} ms that exceed the mean coherence-time of the coherence-time history; and
ii) specifying the largest value among the selected values exceeding the mean coherence-time as the periodicity of t 2 milliseconds for transmitting the SSBs in the optimal set of beam directions as well as in the complementary set of beam directions.
15 . The method according to claim 12 , wherein the periodicity of t 2 milliseconds for transmitting the SSBs in the optimal set of beam directions as well as in the complementary set of beam directions is determined from the at least one of the previously obtained doppler-spread and coherence-time history, and wherein the periodicity of t 1 milliseconds for transmitting the SSBs in the optimal set of beam directions and the periodicity of t 2 milliseconds for transmitting the SSBs in the optimal set of beam directions as well as in the complementary set of beam directions are determined as follows:
i) selecting values from the periodicity set of {5,10, 20, 40, 80, 160} ms that exceed the mean coherence-time of the coherence-time history;
ii) specifying the smallest value among the selected values exceeding the mean coherence-time as the periodicity of t 1 milliseconds for transmitting the SSBs in the optimal set of beam directions; and
iii) specifying the largest value among the selected values exceeding the mean coherence-time as the periodicity of t 2 milliseconds for transmitting the SSBs in the optimal set of beam directions as well as in the complementary set of beam directions.