Timing requirement dependent search space configuration for MTC devices of different categories

A method of controlling radio transmission in a wireless communication network, the method comprising:

• depending on a timing requirement for a radio device, the radio device selecting at least one of a first search space configuration and a second search space configuration;
• an access node determining a number of radio devices of the first class in a coverage region of the access node;
• and
• the access node determining the configuration of at least one of the first search space and the second search space depending on the determined number of radio devices of the first class;
• wherein:
• the first search space configuration defines a first search space in terms of first time domain coordinates and first frequency domain coordinates of a time-frequency grid of radio resource elements;
• and
• the second search space configuration defines a second search space in terms of second time coordinates and second frequency domain coordinates of the time frequency grid, the second search space differing from the first search space at least with respect to the time domain coordinates;
• if the first search space configuration is selected, the radio device receiving downlink control information in radio resource elements of the first search space;
• and
• if the second search space configuration is selected, the radio device receiving downlink control information in radio resource elements of the second search space.

An access node for a wireless communication network, the access comprising:

• processing circuitry;
• memory containing instructions executable by the processing circuitry whereby the access node is operative to:
• determine a configuration of a first search space in terms of first time domain coordinates and first frequency domain coordinates of a time-frequency grid of radio resource elements;
• determine a configuration of a second search space in terms of second time coordinates and second frequency domain coordinates of the time frequency grid, the second search space differing from the first search space at least with respect to the time domain coordinates;
• determine a number of radio devices of the first class in a coverage region of the access node;
• determine the configuration of at least one of the first search space and the second search space depending on the determined number of radio devices of the first class;
• in radio resource elements of the first search space, transmit downlink control information for a first class of radio devices subject to a first timing requirement;
• and
• in radio resource elements of the second search space, transmit downlink control information for a second class of radio devices subject to a second timing requirement which is stricter than the first timing requirement.