Random access method for wireless communication systems

1 . A method for establishing random access communications between a base station and one or more mobile terminals, the method comprising:

configuring one or more uplink random access opportunities based on time and frequency variables;

broadcasting the uplink random access opportunities;

monitoring the uplink random access opportunities for detecting a random access request; and

providing one or more down link access channels to the mobile terminals making the random access requests,

wherein random access requests from multiple mobile terminals occupy different uplink random access opportunities or are modulated by different modulation sequences for reducing collision.

2 . The method of claim 1 further comprising:

choosing an uplink random access opportunity by a mobile terminal;

choosing a modulation sequence by the mobile terminal;

modulating a random access request with preamble and request header with the modulation sequence by the mobile terminal; and

transmitting the modulated random access request to the base station by the mobile terminal.

3 . The method of claim 2 , wherein the random access request further includes a pilot.

4 . The method of claim 1 , wherein the providing further includes:

extracting identity information of the mobile terminal from the random access request; and

providing the downlink access channel to the mobile terminal associated with the identity information.

5 . The method of claim 4 , wherein the extracting further includes performing predetermined correlation on the received random access request signal.

6 . The method of claim 5 , wherein a cyclic correlation of received random access requests is performed to identify different peaks in a frequency domain corresponding to different preambles of the requests.

7 . The method of claim 1 , wherein the broadcasting further includes broadcasting a predetermined prototype modulation sequence based on which the modulation sequences are derived.

8 . The method of claim 6 , wherein the modulation sequences are time shifted versions of the prototype modulation sequence.

9 . The method of claim 1 , wherein two mobile terminals sharing the same random access opportunity have different modulation sequences.

10 . A method for establishing random access communications between a base station and one or more mobile terminals, the method comprising:

configuring one or more uplink random access opportunities based on time and frequency variables;

broadcasting the uplink random access opportunities;

monitoring the uplink random access opportunities chosen by one or more mobile terminals for detecting a random access request therefrom; and

providing one or more down link access channels to the mobile terminals making the random access requests,

wherein random access requests from multiple mobile terminals occupy different uplink random access opportunities for reducing collision.

11 . The method of claim 10 further comprising:

choosing an uplink random access opportunity by a mobile terminal;

choosing a modulation sequence by the mobile terminal;

modulating a random access request with preamble and request header with the modulation sequence by the mobile terminal; and

transmitting the modulated random access request to the base station by the mobile terminal.

12 . The method of claim 11 , wherein the random access request further includes a pilot.

13 . The method of claim 10 , wherein the providing further includes:

extracting identity information of the mobile terminal from the random access request; and

providing the downlink access channel to the mobile terminal associated with the identity information.

14 . The method of claim 13 , where the extracting further includes performing predetermined correlation on the received random access request signal.

15 . A method for establishing random access communications between a base station and one or more mobile terminals, the method comprising:

configuring one or more uplink random access opportunities based on time and frequency variables;

broadcasting the uplink random access opportunities;

monitoring the uplink random access opportunities for detecting a random access request; and

providing one or more down link access channels to the mobile terminals making the random access requests,

wherein random access requests from multiple mobile terminals share the same random access opportunity but are modulated by different modulation sequences for reducing collision.

16 . The method of claim 15 further comprising:

choosing an uplink random access opportunity by a mobile terminal;

choosing a modulation sequence by the mobile terminal;

modulating a random access request with preamble and request header with the modulation sequence by the mobile terminal; and

transmitting the modulated random access request to the base station by the mobile terminal.

17 . The method of claim 16 , wherein the random access request further includes a pilot.

18 . The method of claim 15 , wherein the providing further includes:

extracting identity information of the mobile terminal from the random access request; and

providing the downlink access channel to the mobile terminal associated with the identity information.

19 . The method of claim 18 , wherein the extracting further includes performing predetermined correlation on the received random access request signal.

20 . The method of claim 19 , wherein a cyclic correlation of received random access requests is performed to identify different peaks in a frequency domain corresponding to different preambles of the requests.

21 . The method of claim 15 , wherein the broadcasting further includes broadcasting a predetermined prototype modulation sequence based on which the modulation sequences are derived.

22 . The method of claim 21 , wherein the modulation sequences are time shifted versions of the prototype modulation sequence.