Method and arrangement for improved relaying

1. A method for communication in a wireless communication relay system having a number of network nodes, said system comprising a transmitting node, at least one relaying node, and at least one receiving node, each node with at least one antenna, wherein said method comprises the steps of:

said transmitting node forming at least one OFDM symbol; and

said transmitting node transmitting a signal comprising said at least one OFDM symbol to the at least one relaying node and directly to the at least one receiving node,

said transmitting node configuring a cyclic prefix for said OFDM symbol, wherein the time duration of said cyclic prefix is larger than a predetermined parameter based on a power delay profile of an equivalent channel of said relayed signal and said direct signal, and wherein said parameter is based on at least one or a combination of a maximum delay spread for each said relayed and direct signal, a maximum delay difference between said relayed and direct signals, and a relay node induced delay said at least one relaying node concurrently, and with a latency substantially smaller than the OFDM symbol duration, receiving and amplifying a representation of said signal, and transmitting said amplified representation as a relayed signal in the same frequency band, and

said at least one receiving node concurrently receiving a superposition of said direct signal and said relayed signal to enable constructive interference for corresponding said at least one OFDM symbol and providing the extracted OFDM symbol substantially free from Inter Symbol Interference.

2. The method according to claim 1 , wherein said predetermined parameter is equal to the sum of the maximum delay spread for each said relayed and direct signal, the maximum delay difference between said relayed and direct signals, and the relay node induced delay.

3. The method according to claim 1 , wherein said wireless communication system is a cooperative relaying system.

4. The method according to claim 3 , wherein said cooperative relaying system is a two-hop system.

5. The method according to claim 1 , wherein said at least one relay node comprises at least one on-frequency repeater.

6. The method according to claim 1 , further comprising canceling, in a subset of the at least one relaying node, the feedback experienced from the transmitted signal at a receiver input of said at least one relay node, through interference cancellation, to enable increased amplification gain in said subset of relay nodes.

7. The method according to claim 1 , wherein said at least one receiving node has a single antenna and said transmitting node has at least one antenna, said method further comprising detecting a phase difference between the relayed signal and the direct signal, and phase shifting said relayed signal based on the detected phase difference, ensuring said signals to be received concurrently and substantially in-phase at said at least one receiving node.

8. The method according to claim 1 , wherein each of said transmitter node and said at least one receiving node comprise multiple antennas and said transmitter node and said at least one receiving node communicating by means of a MIMO communication method, further comprising adapting at least one of the gain and the phase parameters for the forwarded signal in at least one relaying node depending on at least one of the channels between transmitting node-receiving node, transmitting node-relaying node, and relaying node-receiving node.

9. A wireless communication relay system having a number of network nodes, said system comprising a transmitting node, at least one relaying node, and at least one receiving node, each node with at least one antenna, wherein said system comprises:

means, in said transmitting node, for forming at least one OFDM symbol to said at least one relaying node and directly to said at least one receiving node, and

means, in said transmitting node, for transmitting a signal comprising said at least one OFDM symbol to the at least one relaying node and directly to the at least one receiving node,

means for configuring a cyclic prefix for said OFDM symbol, wherein the time duration of said cyclic prefix is larger than a predetermined parameter based on a power delay profile of an equivalent channel of said relayed signal and said direct signal, and wherein said parameter is based on at least one or a maximum delay spread for each said relayed and direct signal, a maximum delay difference between said relayed and direct signals, and a relay node induced delay

means, in said at least one relaying node, for concurrently, and with a latency substantially smaller than the OFDM symbol duration, receiving and amplifying a representation of said signal, and

means in said at least one relaying node, for transmitting said amplified representation as a relayed signal in the same frequency band, and

means, in said at least one receiving node, for concurrently receiving a superposition of said direct signal and said relayed signal to enable constructive interference for corresponding said at least one OFDM symbol and providing the extracted OFDM symbol substantially free from Inter Symbol Interference.

10. The system according to claim 9 , wherein said predetermined parameter is equal to the sum of the maximum delay spread for each said relayed and direct signal, the maximum delay difference between said relayed and direct signals, and the relay node induced delay.

11. The system according to claim 9 , wherein said wireless communication system is a cooperative relaying system.

12. The system according to claim 11 , wherein said cooperative relaying system is a two-hop system.

13. The system according to claim 9 , wherein said at least one relay node comprises at least one on-frequency repeater.

14. The system according to claim 9 , wherein a subset of the at least one relaying node is configured to cancel the feedback experienced from the transmitted signal at the receiver input of said relaying node through interference cancellation, to enable increased amplification gain in said one or a subset of nodes.

15. The system according to claim 11 wherein said at least one receiving node has a single antenna and said transmitting node has at least one antenna, further comprising means for detecting a phase difference between the relayed signal and the direct signal, and means for phase shifting said relayed signal based on the detected phase difference, ensuring said signals to be received concurrently and substantially in-phase at the receiving node.

16. The system according to claim 11 wherein each of said transmitter node and said at least one receiving node comprise multiple antennas and said transmitter node and said at least one receiving node communicating by means of a MIMO communication method, further comprising means for adapting at least one of the gain and the phase parameters for the forwarded signal in at least one relaying node depending on at least one of the channels between transmitting node-receiving node, transmitting node-relaying node and relaying node-receiving node.