Information transmission in random access

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 are configured to, with the at least one processor, cause the apparatus to:

select, at a terminal device, one of a plurality of random access preambles, the plurality of random access preambles being divided into a plurality of subsets of random access preambles;

select at least one predefined sequence associated with the selected random access preamble based on a predetermined association between a plurality of predefined sequences and the plurality of subsets of random access preambles and based on a target resource unit to be used for transmission of control information and data information of variable size, wherein the control information indicates a number of resource units for transmitting the data information;

modulate the control information with one of the at least one predefined sequence, the control information indicating configuration of the data information;

in response to the number of resource units, indicated by the control information, for transmitting the data information being larger than one, map the data information to the number of resource units, of a series of repeating resource units, in a cyclic order starting from the target resource unit, and when mapping of the data information to the number of the resource units reaches a last resource unit of the series of repeating resource units before mapping of the data information is completed, the mapping of the data information continues in the cyclic order to a first resource unit of the series of repeating resource units; and

transmit the selected random access preamble, the control information, and the data information in a random access message to a network device, the data information being transmitted using the number of resource units.

2. The apparatus of claim 1 , wherein the plurality of predefined sequences are orthogonal or quasi-orthogonal to each other.

3. The apparatus of claim 1 , wherein the at least one processor and the computer program code are configured to further cause the apparatus to:

receive, from the network device, allocation of resource units for transmission of the data information based on a location of the target resource unit and the number of resources units.

4. The apparatus of claim 1 , wherein the at least one processor and the computer program code are configured to cause the apparatus to:

if there are not enough resource units for transmission of the data information, map the data information to at least one additional resource unit to satisfy the number of resource units.

5. The apparatus of claim 1 , wherein the at least one processor and the computer program code are configured to cause the apparatus to:

modulate the control information with the selected predefined sequence; and

transmit the modulated control information.

6. The apparatus of claim 1 , wherein the control information indicates at least one of a size of the data information, or a modulation coding scheme used for the data information.

7. The apparatus of claim 1 , wherein the at least one processor and the computer program code are configured to cause the apparatus to:

determine a location of a further target resource unit to be used for transmission of the selected random access preamble; and

select the at least one predefined sequence based on the predetermined association that is related to the location of the further target resource unit to be used for transmission of the selected random access preamble.

8. The apparatus of claim 1 , wherein the control information and resource elements carrying the control information are of predetermined sizes, and wherein the data information is of a variable size.

9. The apparatus of claim 1 , wherein the plurality of random access preambles comprise a plurality of sets of random access preambles each associated with a resource unit available for transmission of the control information and the data information, and wherein the at least one processor and the computer program code are configured to further cause the apparatus to:

determine the target resource unit based on the set of random access preambles from which the random access preamble is selected.

10. The apparatus of claim 1 , wherein the at least one processor and the computer program code are configured to further cause the apparatus to:

receive an indication of the predetermined association from the network device.

11. 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 are configured to, with the at least one processor, cause the apparatus to:

detect, at a network device, one of a plurality of random access preambles that is received from a terminal device, the plurality of preambles being divided into a plurality of subsets of random access preambles;

determine at least one predefined sequence associated with the detected random access preamble based on a predetermined association between a plurality of predefined sequences and the plurality of subsets of random access preambles and based on a target resource unit to be used for transmission of control information and data information of variable size from the terminal device, wherein the control information indicates a number of resource units for the data information;

detect the control information on the target resource unit based on the at least one predefined sequence, the control information indicating a configuration of the data information;

detect, based on the control information, the data information on the number of resource units; and

in response to the control information indicating the number of resource units and the number being larger than one, determine the data information from the number of resource units, of a series of repeating resource units, in a cyclic order starting from the target resource unit until reaching a last resource unit of the series of repeating resource, and then continuing in the cyclic order to a first resource unit of the series of repeating resource units to determine the data information.

12. The apparatus of claim 11 , wherein the plurality of predefined sequences are orthogonal or quasi-orthogonal to each other.

13. The apparatus of claim 11 , wherein the control information indicates at least one of a size of the data information, or a modulation coding scheme used for the data information.

14. The apparatus of claim 11 , wherein the control information and resource elements carrying the control information are of predetermined sizes.

15. The apparatus of claim 11 , wherein the plurality of random access preambles comprise a plurality of sets of random access preambles each associated with a resource unit available for transmission of the control information and the data information.

16. A method, comprising:

selecting, at a terminal device, one of a plurality of random access preambles, the plurality of random access preambles being divided into a plurality of subsets of random access preambles;

selecting at least one predefined sequence associated with the selected random access preamble based on a predetermined association between a plurality of predefined sequences and the plurality of subsets of random access preambles and based on a target resource unit to be used for transmission of control information and data information of variable size, wherein the control information indicates a number of resource units for transmitting the data information;

modulating the control information with one of the at least one predefined sequence, the control information indicating configuration of the data information;

in response to the number of resource units, indicated by the control information, for transmitting the data information being larger than one, mapping the data information to the number of resource units, of a series of repeating resource units, in a cyclic order starting from the target resource unit, and when mapping of the data information to the number of the resource units reaches a last resource unit of the series of repeating resource units before mapping of the data information is completed, the mapping of the data information continues in the cyclic order to a first resource unit of the series of repeating resource units; and

transmitting the selected random access preamble, the control information, and the data information in a random access message to a network device, the data information being transmitted using the number of resource units.

17. The method of claim 16 , further comprising:

receiving, from the network device, allocation of resource units for transmission of the data information based on a location of the target resource unit and the number of resource units.