Reserving transmission resources in wireless network

1. A method, comprising:

querying which of a plurality of channels are free via a transmission request message transmitted on the plurality of channels from a first wireless communication apparatus to a second wireless communication apparatus, wherein the transmission request message comprises a duration field that defines a duration of a first reservation period of the plurality of channels;

receiving a transmission response message as a response to the transmission request message, wherein the transmission response message indicates at least one of the plurality of channels the second wireless communication apparatus has detected to be free;

determining a duration of a second reservation period that ends after the first reservation period based on the received transmission response message, wherein the second reservation period extends to cover a data transmission, and wherein the duration of the second reservation period is determined to be longer in a case where not all of the plurality of channels are detected to be free than in a case where all of the plurality of channels are detected to be free; and

causing the first wireless communication apparatus to reserve the at least one of the plurality of channels detected to be free for the second reservation period and to transmit data during the second reservation period.

2. The method of claim 1 , wherein the transmission of the transmission request message and the reception of the transmission response message are carried out during a probing phase, wherein the duration of the first reservation period is confined to the probing phase, and wherein the duration of the second reservation period extends to protect the data transmission.

3. The method of claim 1 , further comprising:

in response to the reception of the transmission response message, determining based on a number of the at least one of the plurality of channels detected to be free to proceed to the data transmission and to carry out the reservation of the at least one of the plurality of channels detected to be free and to the determination of the duration of the second reservation period.

4. The method of claim 1 , further comprising:

computing the duration of the second reservation period based on a number of the at least one of the plurality of channels detected to be free with respect to a number of the plurality of channels on which the transmission request message was transmitted;

causing the first wireless communication apparatus to transmit a second transmission request message comprising an information element identifying the duration of the second reservation period;

receiving a second transmission response message from the second wireless communication apparatus in response to the second transmission request message; and

in response to the reception of the second transmission response message, causing the first wireless communication apparatus to transmit the data to the second wireless communication apparatus during the second reservation period.

5. The method of claim 1 , further comprising:

reading the duration of the second reservation period from the received transmission response message;

computing a currently remaining duration of the second reservation period; and

causing the first wireless communication apparatus to transmit another transmission response message destined to the first wireless communication apparatus itself and comprising an information element identifying the currently remaining duration of the second reservation period, thereby effecting reservation of the at least one of the plurality of channels detected to be free in a coverage area of the first wireless communication apparatus.

6. A method, comprising:

receiving, in a wireless communication apparatus, a transmission request message on at least one channel, wherein the transmission request message is used to query which of a plurality of channels is free, and wherein the transmission request message comprises a duration field that defines a duration of a first reservation period of the plurality of channels;

determining a duration of a second reservation period that ends after the first reservation period, wherein the second reservation period extends to cover a data transmission, and wherein the duration of the second reservation period is determined to be longer in a case where not all of the plurality of channels are detected to be free than in a case where all of the plurality of channels are detected to be free; and

causing the wireless communication apparatus to transmit a transmission response message as a response to the query of the transmission request message, wherein the transmission response message indicates at least one of the plurality of channels detected to be free, wherein the at least one of the plurality of channels detected to be free is reserved for the data transmission during the second reservation period.

7. The method of claim 6 , wherein the reception of the transmission request message and the transmission of the transmission response message are carried out during a probing phase, wherein the duration of the first reservation period is confined to the probing phase, and wherein the duration of the second reservation period extends to protect the data transmission.

8. The method of claim 6 , further comprising:

computing the duration of the second reservation period based on a number of the at least one of the plurality of channels detected to be free with respect to a number of the plurality of channels queried with the transmission request message; and

transmitting in the transmission response message an information element identifying the duration of the second reservation period.

9. An apparatus comprising:

at least one processor; and

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

query which of a plurality of channels are free via transmitting a transmission request message to a wireless communication apparatus on the plurality of channels, wherein the transmission request message comprises a duration field that defines a duration of a first reservation period of the plurality of channels;

receive a transmission response message as a response to the transmission request message, wherein the transmission response message indicates at least one of the plurality of channels the wireless communication apparatus has detected to be free;

determine a duration of a second reservation period that ends after the first reservation period based on the received transmission response message, wherein the second reservation period extends to cover a data transmission, and wherein the duration of the second reservation period is determined to be longer in a case where not all of the plurality of channels are detected to be free than in a case where all of the plurality of channels are detected to be free; and

reserve the at least one of the plurality of channels detected to be free for the duration of the second reservation period and to transmit data during the second reservation period.

10. The apparatus of claim 9 , wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to carry out the transmission of the transmission request message and the reception of the transmission response message during a probing phase, wherein the duration of the first reservation period is confined to the probing phase, and wherein the duration of the second reservation period extends to protect the data transmission.

11. The apparatus of claim 9 , wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to, in response to the reception of the transmission response message, determine based on a number of the at least one of the plurality of channels detected to be free whether or not to proceed to the data transmission and to carry out the reservation of the at least one of the plurality of channels detected to be free and the determination of the duration of the second reservation period.

12. The apparatus of claim 9 , wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to:

compute the duration of the second reservation period based on a number of the at least one of the plurality of channels detected to be free with respect to a number of the plurality of channels on which the transmission request message was transmitted;

transmit a second transmission request message comprising an information element identifying the duration of the second reservation period;

receive a second transmission response message from the wireless communication apparatus in response to the second transmission request message; and

in response to the reception of the second transmission response message, transmit data to the wireless communication apparatus during the second reservation period.

13. The apparatus of claim 9 , wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to:

read the duration of the second reservation period from the received transmission response message;

compute a currently remaining duration of the second reservation period; and

transmit another transmission response message destined to the apparatus itself and comprising an information element identifying the currently remaining duration of the second reservation period, thereby effecting reservation of the at least one of the plurality of channels detected to be free in a coverage area of the apparatus.

14. The apparatus of claim 9 , further comprising radio interface components providing the apparatus with radio communication capability.

15. An apparatus comprising:

at least one processor; and

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

receive a transmission request message on at least one channel, wherein the transmission request message is used to query which of a plurality of channels is free, and wherein the transmission request message comprises a duration field that defines a duration of a first reservation period of the plurality of channels;

determine a duration of a second reservation period that ends after the first reservation period, wherein the second reservation period extends to cover a data transmission, and wherein the duration of the second reservation period is determined to be longer in a case where not all of the plurality of channels are detected to be free than in a case where all of the plurality of channels are detected to be free; and

transmit a transmission response message as a response to the query of the transmission request message, wherein the transmission response message indicates at least one of the plurality of channels detected to be free, wherein the at least one of the plurality of channels detected to be free is reserved for the data transmission during the second reservation period.

16. The apparatus of claim 15 , wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to carry out the reception of the transmission request message and the transmission of the transmission response message during a probing phase, wherein the duration of the first reservation period is confined to the probing phase, and wherein the duration of the second reservation period extends to protect the data transmission.

17. The apparatus of claim 15 , wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to:

compute the duration of the second reservation period based on a number of the at least one of the plurality of channels detected to be free with respect to a number of the plurality of channels queried with the transmission request message; and

transmit in the transmission response message an information element identifying the duration of the second reservation period.

18. The apparatus of claim 15 , wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to:

receive in the transmission request message an information element commanding the apparatus to compute the duration of the second reservation period; and

in response to the reception of the information element, compute the duration of the second reservation period and transmit the transmission response message identifying the duration of the second reservation period.