Method and apparatus for supporting direct link communication in tdd cdma system

• US 20060245398A1
• Filed: 03/29/2004
• Published: 11/02/2006
• Est. Priority Date: 04/11/2003
• Status: Active Grant

• Current Assignee: Pendragon Wireless LLC (Pendrell Corporation)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Li, Yueheng, Li, Sun
• Granted Patent: US 7,286,842 B2
• Time in Patent Office: Days
• US Class Current: 370/335
• CPC Class Codes: H04B 7/2668 Arrangements for Wireless Code-Division Multiple Access [CDMA] System Synchronisation, for code acquisition H04B1/7075, for code tracking H04B1/7085
• CPC Class Codes: H04J 13/004 Orthogonal
• CPC Class Codes: H04W 48/10 using broadcasted information
• CPC Class Codes: H04W 52/383 power control in peer-to-peer links
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 84/04 Large scale networks; Deep hierarchical networks

Abstract

A method for supporting P2P communication between two user equipments in TDD CDMA systems, performed by user equipment, comprising: receiving signals transferred via the downlink control channel from network system; acquiring the timeslot allocation information and the spreading code allocation information of other active user equipments allocated in the specific downlink timeslot associated with the direct link used by said user equipments, according to the received signals; and synchronizing the P2P communication signals received by the user equipment and signals from network system, according to the acquired timeslot allocation information and spreading code allocation information, so as to reduce the interference caused by the downlink signals transmitted from network system to other user equipments during the P2P communication process.

Claims

1. A method for supporting P2P (Peer to Peer) communication between two user equipments in TDD CDMA systems, performed by user equipment, comprising:

receiving signals transferred via the downlink control channel by network system;

acquiring the timeslot allocation information according to the received signals;

acquiring the spreading code allocation information of other active user equipments allocated in the specific downlink timeslot associated with the direct link used by said user equipments, according to the received signals; and

reducing the interference caused by signals transferred via downlink from network system to said other user equipments during P2P communication according to the acquired timeslot allocation information and spreading code allocation information.

2. The communication method according to claim 1, wherein said spreading code allocation information at least includes the said spreading code information being used by other user equipments in said downlink timeslot.

3. The communication method according to claim 1, wherein said step of reducing the interference includes executing at least one of the methods Multi-User Detection (MUD) and Joint Detection (JD).

4. The communication method according to claim 3, wherein at least one of said methods Multi-User Detection (MUD) and Joint Detection (JD) utilizes said spreading code information being used by other user equipments in said downlink timeslot to reduce interference.

5. The communication method according to claim 4, further comprising:

establishing downlink synchronization with network system at the cell search phase, and keeping downlink synchronization with network system by tracking the pilot channel;

In said downlink timeslot, when said user equipments transmitting signals via said direct link, the steps taken by said user equipment comprises;

(i) during establishing said direct link, setting the time of transmitting signals to the other user equipment in said downlink timeslot, according to the received time of transmitting signals by network system;

(ii) transmitting test signals to the other user equipment at said set time in said downlink timeslot;

(iii) receiving feedback signal from the other user equipment, which is the time difference obtained by comparing the time at which the other user equipment receives the test signals and the received time at which the network system transmits signals in the other user equipment, after the other user equipment receiving said test signals;

(iv) setting the time advance for transmitting signals to the other user equipment according to the feedback signals; and

(v) adjusting the time at which the user equipment transmits signals to the other user equipment according to time advance, in order that the signals of downlink from network system, which are received by the other user equipment, are synchronized with the signals of said direct link from the user equipment.

6. The communication method according to claim 5, further includes:

(vi) transmitting the P2P communication signals to said the other user equipment at said adjusted time for transmitting;

(vii) receiving the synchronization shift information from said the other user equipment, which is the synchronization derivation estimated according to received the P2P communication signals in said the other user equipment after receiving said P2P communication signals; and

(viii) adjusting the timing advance for transmitting signals to the other user equipment according to the synchronization shift information.

7. The communication method according to claim 5, further includes:

adjusting the time at which the user equipment transmits signals to the other user equipment during the P2P communication procedure, according to the synchronization shift information from the other user equipment, in order that the P2P communication signals transmitted by the user equipment and the downlink signals transmitted by network system can reach the other user equipment at the same time.

8. The communication method according to claim 5, wherein when the user equipment receives signals via said direct link in said downlink timeslot, the step to be taken includes:

(a) calculating the difference between the time for receiving the test signals transmitted from the other user equipment and the time for receiving the signals transmitted from network system, and sends the calculated time difference as feedback signals to the other user equipment, when receiving test signals transmitted by said the other user equipment, during the process of establishing said direct link.

9. The communication method according to claim 8, wherein when the user equipment receives signals via said direct link in said downlink timeslot, the step to be taken further includes:

(b) estimating the synchronization shift information of the other user equipment according to the received P2P communication signals when the UE receives the P2P communication signals transmitted by the other user equipment, and sending the estimated synchronization shift information to the other one, during the process of establishing the said direct link.

10. The communication method according to claim 8, further includes:

calculating the synchronization shift information of the other user equipment according to the received P2P communication signals from said the other user equipment, and sending the synchronization shift information to the other one, during the process of P2P communication.

11. A method for supporting P2P communication between two user equipments in TDD CDMA systems, the steps taken by network system comprising:

sending the timeslot allocation information to the two users equipment conducting P2P communication via downlink control channel;

generating spreading code allocation information corresponding to each downlink timeslot of timeslot allocation information; and

sending said spreading code allocation information to the two user equipments via downlink control channel respectively, in order to synchronize the P2P communication signals received by each of the two UE with the signals from network system.

12. The communication method according to claim 11, wherein said spreading code allocation information at least includes spreading code information being used by other user equipments in said downlink timeslot.

13. A user equipment for supporting P2P (Peer to Peer) communication in TDD CDMA systems, comprising:

a signal transceiver, for receiving and transmitting radio signals;

a timeslot allocation information acquiring means for acquiring the timeslot allocation information according to the information transferred via downlink control channel;

a spreading code allocation information acquiring means for acquiring the spreading code allocation information of other active user equipments in a specific downlink timeslot which is used when the UE is receiving signals via the direct link between the UE and the other one, according to the information transferred via downlink control channel; and

a interference reducing means for reducing the interference caused by downlink signals transmitted from network system to other user equipments during P2P communication process according to the acquired timeslot allocation information and spreading code allocation information.

14. The user equipment according to claim 13, wherein said spreading code allocation information at least includes the spreading code information being used by other user equipments in said downlink timeslot.

15. The user equipment according to claim 13 , wherein said interference reducing means executes at least one of the methods Multi-User Detection (MUD) and Joint Detection (JD ) to reduce interference.

16. The user equipment according to claim 15, wherein one of said methods Multi-User Detection (MUD) and Joint Detection (JD) reduce interference by using said spreading code information being used by other user equipments in said downlink timeslot.

17. The user equipment according to claim 16, further including:

a synchronization means, for establishing downlink synchronization with network system at the cell search phase, and keeping downlink synchronization with the network system by tracking the pilot channel;

a transmitting time setting means, for setting the time for transmitting signals to the other user equipment in said downlink timeslot , according to the time for receiving the transmitting signals from the network system, in the process of establishing the said direct link;

a test signals transmitting means, for transmitting test signals to the other user equipment at the set time in said downlink timeslot;

a feedback signal receiving means, for receiving feedback signals from the other user equipment, which is the time difference obtained by comparing the time for receiving test signals and the time for receiving the transmitting signals from the network system in the other user equipment, after the other user equipment receiving the test signals;

a time advance setting means for setting the time advance for transmitting signals to the other user equipment; and

a transmitting time adjusting means based on said feedback signals, for adjusting the transmitting time at which the user equipment transmits signals to the other user equipment according to the time advance, in order that the signals transferred via downlink from network system, which are received by the other user equipment, are synchronized with the signals transferred via said direct link from said user equipment.

18. The user equipment according to claim 17, further includes:

a synchronization shift information receiving means, for receiving the synchronization shift information from said the other user equipment, which is the synchronization derivation estimated by the other user equipment after receiving P2P communication signals, according to the received P2P communication signals; and

a transmitting time adjusting means based on synchronization shift information, for adjusting the timing advance for transmitting signals to said the other user equipment according to said synchronization shift information.

19. The user equipment according to claim 17 , further includes:

a feedback signals generating means, for calculating the difference between the time for receiving test signals and the time for receiving signals transmitted from network system, and sending the calculated difference as feedback signals to the other user equipment when receiving the test signals transmitted by the other user equipment, during the process of establishing said direct link.

20. The user equipment according to claim 19, further includes:

a synchronization shift information generating means, for estimating the synchronization shift information of the other user equipment according to the P2P communication signals when the UE receives P2P communication signals transmitted by said the other user equipment, and sending the estimated synchronization shift information to the other one.

21. A network system for supporting P2P communication between two user equipments in TDD CDMA systems, comprising:

a timeslot allocation information sending means for sending the timeslot allocation information to the two user equipments in P2P communication via downlink control channel;

a spreading code allocation information generating means for generating the spreading code allocation information corresponding to each downlink timeslot in the timeslot allocation information; and

a spreading code allocation information sending means for sending the spreading code allocation information to the two user equipments via downlink control channel respectively, so as to synchronize the P2P communication signals received by each of the two UEs with signals from network systems.

22. The network system according to claim 21, wherein said spreading codes allocation information at least contains the spreading code information being used by user equipments in said downlink timeslot.