Timing advance calculation

1 . An apparatus comprising:

an antenna system configured to communicate with a further antenna system of a wireless communication system during a transmission frame identifying a plurality of sub-frames;

computation circuitry configured to calculate a timing advance to be applied, by the further antenna system, to modify a time at which uplink data corresponding to a particular sub-frame of the plurality of sub-frames is transmitted by the further antenna system relative to a time at which downlink data corresponding to the particular sub-frame would be received by the further antenna system; and

communication circuitry configured to transmit the timing advance to the further antenna system,

wherein the timing advance is restricted to a predefined range, and the computation circuitry is configured:

to estimate a round trip time for a signal to travel twice a separation distance between the antenna system and the further antenna system;

in response to the round trip time being within the predefined range, to set the timing advance based on the round trip time; and

in response to the round trip time being outside of the predefined range, to set the timing advance to a value within the predefined range, wherein a difference between the value and the round trip time is based on a duration of one or more sub-frames.

2 . The apparatus of claim 1 , wherein the communication circuitry is configured to receive an uplink communication transmitted from the further antenna system during a first predefined sub-frame of the plurality of sub-frames advanced by the timing advance and to transmit information indicative of receipt of the uplink communication during a second predefined sub-frame of the plurality of sub-frames.

3 . The apparatus of claim 2 , wherein an acknowledgement delay between the first predefined sub-frame and the second predefined sub-frame is set based on a maximum operable separation distance between the antenna system and the further antenna system.

4 . The apparatus of claim 3 , wherein the acknowledgement delay is equal to a predefined minimum number of sub-frames plus at least one additional sub-frame for each of the one or more sub-frames on which the duration is based.

5 . The apparatus of claim 3 , wherein a total number of sub-frames in the transmission frame is determined based on the acknowledgement delay and a retransmission delay defined as a default number of sub-frames between the second predefined sub-frame and a next first predefined sub-frame.

6 . The apparatus of claim 5 , wherein at least one of:

the acknowledgement delay comprises a processing time associated with decoding the uplink communication; and

the retransmission delay comprises a processing time associated with decoding the downlink communication.

7 . The apparatus of any of claim 3 , wherein a maximum round trip time for a signal to travel twice the maximum operable distance is greater than the predefined range.

8 . The apparatus of claim 1 , wherein the communication circuitry is configured to transmit a downlink communication to the further antenna system during a third predefined sub-frame of the plurality of sub-frames and to receive information indicative receipt of the downlink communication transmitted from the further antenna system during a fourth predefined sub-frame of the plurality of sub-frames advanced by the timing advance.

9 . The apparatus of claim 8 , wherein:

the communication circuitry is configured to receive an uplink communication transmitted from the further antenna system during a first predefined sub-frame of the plurality of sub-frames advanced by the timing advance and to transmit information indicative of receipt of the uplink communication during a second predefined sub-frame of the plurality of sub-frames; and

the third predefined sub-frame and the fourth predefined sub-frame are separated by a same number of sub-frames as the first predefined sub-frame and the second predefined sub-frame.

10 . The apparatus of claim 1 , wherein in response to the round trip time being outside of the predefined range, the computation circuitry is configured to determine the value by subtracting the duration of one or more sub-frames from the round trip time.

11 . The apparatus of claim 1 , wherein the antenna system and the further antenna system are configured to communicate according to a HARQ process.

12 . The apparatus of claim 11 , wherein the antenna system and the further antenna system are configured to communicate using a plurality of stop-and-wait HARQ processes.

13 . A wireless communication system comprising:

a further antenna system configured to communicate with an antenna system;

communication circuitry configured to control the further antenna system to communicate with the antenna system during a transmission frame identifying a plurality of sub-frames; and

control circuitry responsive to reception, from the antenna system, of information identifying a timing advance, to control the further antenna system to apply the timing advance to modify a time at which uplink data corresponding to a particular sub-frame of the plurality of sub-frames is transmitted by the further antenna system relative to a time at which downlink data corresponding to the particular sub-frame would be received by the further antenna system,

wherein the timing advance is restricted to a predefined range, and the timing advance is calculated by computation circuitry of the antenna system that is configured:

to estimate a round trip time for a signal to travel twice a separation distance between the antenna system and the further antenna system;

in response to the round trip time being within the predefined range, to set the timing advance based on the round trip time; and

in response to the round trip time being outside of the predefined range, to set the timing advance to a value within the predefined range, wherein a difference between the value and the round trip time is based on a duration of one or more sub-frames.

14 . The wireless communication system of claim 13 , wherein the communication circuitry is configured to transmit an uplink communication to the antenna system during a first predefined sub-frame of the plurality of sub-frames advanced by the timing advance and to receive information indicative of receipt of the uplink communication from the antenna system during a second predefined sub-frame of the plurality of sub-frames.

15 . The wireless communication system of claim 14 , wherein an acknowledgement delay between the first predefined sub-frame and the second predefined sub-frame is set based on a maximum operable separation distance between the antenna system and the further antenna system.

16 . The wireless communication system of claim 15 , wherein the acknowledgement delay is equal to a predefined minimum number of sub-frames plus at least one additional sub-frame for each of the one or more sub-frames on which the duration is based.

17 . The wireless communication system of claim 14 , wherein a total number of sub-frames in the transmission frame is determined based on the acknowledgement delay and a retransmission delay defined as a default number of sub-frames between the second predefined sub-frame and a next first predefined sub-frame.

18 . The wireless communication system of claim 13 , wherein the communication circuitry is configured to receive a downlink communication from the antenna system during a third predefined sub-frame of the plurality of sub-frames advanced by the timing advance and to transmit information indicative receipt of the downlink communication transmitted from the antenna system during a fourth predefined sub-frame of the plurality of sub-frames.

19 . A method of operating an apparatus comprising an antenna system configured to communicate with a further antenna system of a wireless communication system during a transmission frame identifying a plurality of sub-frames, wherein the method comprises:

calculating a timing advance to be applied, by the further antenna system, to modify a time at which uplink data corresponding to a particular sub-frame of the plurality of sub-frames is transmitted by the further antenna system relative to a time at which downlink data corresponding to the particular sub-frame would be received by the further antenna system, wherein the timing advance is restricted to a predefined range;

transmitting the timing advance to the further antenna system;

estimating a round trip time for a signal to travel twice a separation distance between the antenna system and the further antenna system;

in response to the round trip time being within the predefined range, setting the timing advance based on the round trip time; and

in response to the round trip time being outside of the predefined range, setting the timing advance to a value within the predefined range, wherein a difference between the value and the round trip time is based on a duration of one or more sub-frames.

20 . A method of operating a wireless communication system comprising a further antenna system configured to communicate with an antenna system, the method comprising:

controlling the further antenna system to communicate with the antenna system during a transmission frame identifying a plurality of sub-frames; and

in response to reception, from the antenna system, of information identifying a timing advance, controlling the further antenna system to apply the timing advance to modify a time at which uplink data corresponding to a particular sub-frame of the plurality of sub-frames is transmitted by the further antenna system relative to a time at which downlink data corresponding to the particular sub-frame would be received by the further antenna system,

wherein the timing advance is restricted to a predefined range, and the timing advance is calculated, at the antenna system by:

estimating a round trip time for a signal to travel twice a separation distance between the antenna system and the further antenna system;

in response to the round trip time being within the predefined range, setting the timing advance based on the round trip time; and

in response to the round trip time being outside of the predefined range, setting the timing advance to a value within the predefined range, wherein a difference between the value and the round trip time is based on a duration of one or more sub-frames.