Random access channel occasion configuration for message 1 repetitions

1 . An apparatus comprising:

at least one processor; and

at least one memory including computer program code,

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to:

determine, by a user equipment of a communication network, random access channel parameters for random access to the communication network;

based on the random access channel parameters, derive a set of random access channel occasions in a time domain and frequency domain;

based on the derived set of random access channel occasions, map at least one synchronization signal block index to a number of at least one random access channel occasion of the set of random access channel occasions in the time domain and the frequency domain; and

send towards a network node of the communication network Msg1 preamble repetitions using at least part of the number of at least one random access channel occasions,

wherein the mapping is based on a time extension that limits the mapping of the at least one synchronization signal block index in the time domain and is expressed as a number of symbols and slots;

wherein the random access channel parameters comprise a number of consecutive random access channel occasions to map to a predetermined synchronization signal block index and a maximum number of repetitions for a predetermined synchronization signal block index;

wherein more than one random access channel occasion of the set of random access channel occasions is configured in the frequency domain for a same time instance in the time domain;

wherein when the mapping reaches the time extension, the mapping continues in at least one random access channel occasion within the time extension in another frequency different from the frequencies used before reaching the time extension; and

wherein the mapping is derived from an initial mapping and the random access channel parameters comprise a stretching parameter and the initial mapping is stretched in time according to the stretching parameter to derive the mapping.

2 . The apparatus of claim 1 , wherein the mapping is performed in the time domain in at least one random access channel occasion centered on at least one frequency in the frequency domain.

3 . The apparatus of claim 1 , wherein the mapping is performed in the time domain in different frequencies in the frequency domain.

4 . The apparatus of claim 1 , wherein an initial mapping is performed first in the frequency domain and then in the time domain in at least one random access channel occasion, and wherein the mapping is derived from the initial mapping.

5 . The apparatus of claim 1 , wherein the random access channel parameters comprise an indication of a number of synchronization signal block indexes to map per random access channel occasion.

6 . The apparatus of claim 1 , wherein the random access channel parameters comprise an indication of a number of preambles per synchronization signal block index.

7 . The apparatus of claim 1 , wherein more than one random access channel occasion of the set of random access channel occasions is configured in the frequency domain for a same time instance in the time domain, and

wherein a first number of the more than one random access channel occasion configured for a same time instance in the frequency domain is used for the initial mapping and another number of the more than one random access channel occasion is used when the mapping has reached the time extension.

8 . The apparatus of claim 1 , wherein, based on determining that mapped random access channel occasions do not entirely fit within the time extension, the apparatus stops mapping in the time domain and continues mapping in the frequency domain in the first random access channel occasion in the frequency domain from slot number 0 of a first frame.

9 . The apparatus of claim 1 , wherein the random access channel parameters comprise an indication of a number of synchronization signal block indexes to map per random access channel occasion and a number of preambles per synchronization signal block index.

10 . The apparatus of claim 1 , wherein the time extension is further characterized by a time offset and periodicity, the time offset defined as the time of the first occurrence of the time extension and the periodicity defined as the number of symbols and slots between the start of one time extension and the start of a next time extension.

11 . The apparatus of claim 1 , wherein the time extension is one of pre-determined by the user equipment or received from the communication network.

12 . The apparatus of claim 1 , wherein the mapping is performed in the time domain in at least one random access channel occasion centered on at least one frequency in the frequency domain.

13 . The apparatus of claim 1 , wherein the random access channel parameters comprise an indication of a number of synchronization signal block indexes to map per random access channel occasion.

14 . The apparatus of claim 1 , wherein the random access channel parameters comprise an indication of a number of preambles per synchronization signal block index.

15 . The apparatus of claim 1 , wherein, based on determining that mapped random access channel occasions do not entirely fit within the time extension, the apparatus stops mapping in the time domain and continues mapping in the frequency domain, in the first random access channel occasion in the frequency domain from slot 0 of a first frame.

16 . A method, comprising:

determining, by a user equipment of a communication network, random access channel parameters for random access to the communication network;

based on the random access channel parameters, deriving a set of random access channel occasions in a time domain and frequency domain;

based on the derived set of random access channel occasions, mapping at least one synchronization signal block index to a number of at least one random access channel occasion of the set of random access channel occasions in at least one of the time domain or the frequency domain, wherein the mapping is based on a time extension; and

sending towards a network node of the communication network Msg1 preamble repetitions using at least part of the number of at least one random access channel occasions,

wherein the mapping is based on a time extension that limits the mapping of the at least one synchronization signal block index in the time domain and is expressed as a number of symbols and slots;

wherein the random access channel parameters comprise a number of consecutive random access channel occasions to map to a predetermined synchronization signal block index and a maximum number of repetitions for a predetermined synchronization signal block index;

wherein more than one random access channel occasion of the set of random access channel occasions is configured in the frequency domain for a same time instance in the time domain;

wherein when the mapping reaches the time extension, the mapping continues in at least one random access channel occasion within the time extension in another frequency different than the different frequencies in the frequency domain; and

wherein the random access channel parameters comprise a stretching parameter and the initial mapping is stretched in time according to the stretching parameter to derive the mapping.

17 . An apparatus comprising:

at least one processor; and

at least one memory including computer program code,

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to:

determine, by a network node of a communication network, random access channel parameters for random access to the communication network;

based on the random access channel parameters, derive a set of random access channel occasions in a time domain and frequency domain;

wherein based on the derived set of random access channel occasions, there is mapping at least one synchronization signal block index to a number of at least one random access channel occasion of the set of random access channel occasions in at least one of the time domain or the frequency domain, wherein the mapping is based on a time extension; and

based on the mapping, receive from a user equipment of the communication network Msg1 preamble repetitions using at least part of the number of at least one random access channel occasions,

wherein the mapping is based on a time extension that limits the mapping of the at least one synchronization signal block index in the time domain and is expressed as a number of symbols and slots;

wherein the random access channel parameters comprise a number of consecutive random access channel occasions to map to a predetermined synchronization signal block index and a maximum number of repetitions for a predetermined synchronization signal block index;

wherein more than one random access channel occasion of the set of random access channel occasions is configured in the frequency domain for a same time instance in the time domain;

wherein when the mapping reaches the time extension, the mapping continues in at least one random access channel occasion within the time extension in another frequency different than the different frequencies in the frequency domain; and

wherein the random access channel parameters comprise a stretching parameter and the initial mapping is stretched in time according to the stretching parameter to derive the mapping.

18 . The apparatus of claim 17 , wherein the mapping is performed in the time domain in at least one random access channel occasion centered on at least one frequency in the frequency domain.

19 . The apparatus of claim 17 , wherein an initial mapping is performed first in the frequency domain and then in the time domain in at least one random access channel occasion, and wherein the mapping is derived from the initial mapping.