RELAY SYSTEM AND METHOD IN A COMMUNICATION SYSTEM

• US 20080056175A1
• Filed: 09/06/2007
• Published: 03/06/2008
• Est. Priority Date: 09/06/2006
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: JUNG, Young-Ho, KIM, Yung-Soo, YOU, Cheol-Woo
• Granted Patent: US 8,023,445 B2
• Time in Patent Office: Days
• US Class Current: 370/315
• CPC Class Codes: H04B 7/155 Ground-based stations H04B7/204 takes precedence
• CPC Class Codes: H04B 7/2606 Arrangements for base station coverage control, e.g. by using relays in tunnels
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0032 Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver

Abstract

Provided are a relaying method and system in a communication system having a BS, a MS for communicating with the BS, and an RS for relaying signals between the BS and the MS, in which the RS receives a first pilot sequence from the BS, replaces the first pilot sequence with a second pilot sequence, and transmits the second pilot sequence to the MS. Here, a partial cross correlation between the first and second pilot sequences is always ‘0’.

Claims

1. A relaying method in a Relay Station (RS) in a communication system having a Base Station (BS), a Mobile Station (MS) for communicating with the BS, and the RS for relaying signals between the BS and the MS, comprising:

receiving a first pilot sequence from the BS; and

replacing the first pilot sequence with a second pilot sequence and transmitting the second pilot sequence to the MS,

wherein a partial cross correlation between the first and second pilot sequences is always ‘

0’

.

2. The relaying method of claim 1, wherein the RS use full duplex relay scheme.

3. The relaying method of claim 1, further comprising relaying a signal received from the BS that has transmitted the first pilot sequence in a Decode-and-Forward (DF) scheme.

4. The method of claim 1, further comprising performing channel estimation using the first pilot sequence and receiving a signal from the BS using a result of the channel estimation.

5. The method of claim 1, wherein when the BS and the RS use a Single Input Single Output (SISO) scheme, the first and second pilot sequences satisfy the following equation for channel estimation at time t,

P_i,tQ_i,t+P_i,t−

1Q<sub>i,t−

1</sub>=0

where P_i,t denotes a pilot symbol transmitted from the BS on an i^th subcarrier at time t and Q_i,t denotes a pilot symbol transmitted from the RS on the i^th subcarrier at time t.

6. The method of claim 5, wherein each of the first and second pilot sequences is a sequence in the following pilot sequence set,

P_i=└

√

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} 0 . . . ┘


Q_i=[0 √

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} . . . ]
P_i=[1 1 1 1 1 1 1 1 1 1 1 . . . ]
Q_i=[1 −

1 1 −

1 1 −

1 1 −

1 1 −

1 1 −

1 . . . ]

where P₁ denotes a first pilot sequence transmitted on an i^th subcarrier and Q_i denotes a pilot symbol transmitted from the RS on the i^th subcarrier at time t.

7. The method of claim 1, wherein when the BS and the RS use a Multiple Input Multiple Output (MIMO) scheme for M antennas, the first and second pilot sequences satisfy the following equation for channel estimation at time t,

$\sum _{}^{}$

I = 0 2 ⁢

M - 1 ⁢

 

⁢

P i , j ⁡

( t - 1 ) * ⁢

Q i , k ⁡

( t - 1 ) = 0 $\underset{I=0}{\overset{2<br><br>M-1}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>P_{i,j<br><br>\left(t-1\right)}^{*}<br><br>P_{i,k<br><br>\left(t-1\right)}=0,\mathrm{for}<br><br>\text{\hspace{1em}<br><br>}<br><br>j\ne <br><br>k$ $\underset{I=0}{\overset{2<br><br>M-1}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>Q_{i,j<br><br>\left(t-1\right)}^{*}<br><br>Q_{i,k<br><br>\left(t-1\right)}=0,\mathrm{for}<br><br>\text{\hspace{1em}<br><br>}<br><br>j\ne <br><br>k$

where P_i,mt denotes a pilot symbol transmitted from an m^th transmit antenna of the BS on an i^th subcarrier at time t and Q_i,mt denotes a pilot symbol transmitted from an m^th transmit antenna of the RS on the i^th subcarrier at time t.

8. The method of claim 7, wherein when M is 2, each of the first and second pilot sequences is a sequence in the following pilot sequence set,

P_i1=[2 0 0 0 2 0 0 0 2 0 0 0 . . . ]
P_i2=[0 2 0 0 0 2 0 0 0 2 0 0 . . . ]
Q_i1=[0 0 2 0 0 0 2 0 0 0 2 0 . . . ]
Q_i2=[0 0 0 2 0 0 0 2 0 0 0 2 . . . ]
P_i1=[1 1 1 1 1 1 1 1 1 1 1 1 . . . ]
P_i2=[1 −

1 1 −

1 1 −

1 1 −

1 1 −

1 1 −

1 . . . ]
Q_i1=[1 −

1 −

1 1 1 −

1 −

1 1 1 −

1 −

1 1 . . . ]
Q_i2=[1 1 −

1 −

1 1 1 −

1 −

1 1 1 −

1 −

1 . . . ]

where P_i1 denotes a first pilot sequence transmitted on an i^th subcarrier from a first antenna of the BS, P_i2 denotes a first pilot sequence transmitted on the i^th subcarrier from a second antenna of the BS, Q_i1 denotes a second pilot sequence transmitted on the i^th subcarrier from a first antenna of the RS, and Q_i2 denotes a second pilot sequence transmitted on the i^th subcarrier from a second antenna of the RS.

9. The method of claim 7, wherein for at least two antennas in each of the BS and the RS, the first and second pilot sequences are at least one of cyclically shifted sequences and Constant Amplitude and Zero Autocorrelation (CAZAC) sequences of a period determined by the number of the antennas.

10. A relay system in a communication system having a Base Station (BS), a Mobile Station (MS) for communicating with the BS, and an RS for relaying signals between the BS and the MS, comprising:

the RS for receiving a first pilot sequence from the BS, and replacing the first pilot sequence with a second pilot sequence and transmitting the second pilot sequence to the MS,

wherein a partial cross correlation between the first and second pilot sequences is always ‘

0’

.

11. The relay system of claim 10, wherein the RS use full duplex relay scheme.

12. The relay system of claim 10, further comprising the BS for generating and transmitting the first pilot sequence.

13. The relay system of claim 12, wherein the BS comprises a pilot sequence generator for generating the first pilot sequence based on information about the number of antennas.

14. The relay system of claim 10, wherein the RS comprises:

a channel estimator for performing channel estimation using the first pilot sequence;

a data generator for decoding a signal received from the BS that has transmitted the first pilot sequence according to the channel estimation and re-generating data using the decoded signal; and

a pilot sequence generator for generating the second pilot sequence.

15. The relay system of claim 10, wherein the RS relays a signal received from the BS that has transmitted the first pilot sequence in a Decode-and-Forward (DF) scheme.

16. The relay system of claim 10, wherein the RS performs channel estimation using the first pilot sequence and receives a signal from the BS using a result of the channel estimation.

17. The relay system of claim 10, wherein when the BS and the RS use a Single Input Single Output (SISO) scheme, the first and second pilot sequences satisfy the following equation for channel estimation at time t,

P_i,tQ_i,t+P_i,t−

1Q<sub>i,t−

1</sub>=0

where P_i,t denotes a pilot symbol transmitted from the BS on an i^th subcarrier at time t and Q_i,t denotes a pilot symbol transmitted from the RS on the i^th subcarrier at time t.

18. The relay system of claim 17, wherein each of the first and second pilot sequences is a sequence in the following pilot sequence set,

P_i=└

√

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} 0 . . . ┘


Q_i=[0 √

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} 0 √

{square root over (2)} . . . ]
P_i=[1 1 1 1 1 1 1 1 1 1 1 . . . ]
Q_i=[1 −

1 1 −

1 1 −

1 1 −

1 1 −

1 1 −

1 . . . ]

where P_i denotes a first pilot sequence transmitted on an i^th subcarrier and Q_i denotes a pilot symbol transmitted from the RS on the i^th subcarrier at time t.

19. The relay system of claim 10, wherein if the BS and the RS use a Multiple Input Multiple Output (MIMO) scheme for M antennas, the first and second pilot sequences satisfy the following equation for channel estimation at time t,

$\sum _{}^{}$

I = 0 2 ⁢

M - 1 ⁢

 

⁢

P i , j ⁡

( t - 1 ) * ⁢

Q i , k ⁡

( t - 1 ) = 0 $\underset{I=0}{\overset{2<br><br>M-1}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>P_{i,j<br><br>\left(t-1\right)}^{*}<br><br>P_{i,k<br><br>\left(t-1\right)}=0,\mathrm{for}<br><br>\text{\hspace{1em}<br><br>}<br><br>j\ne <br><br>k$ $\underset{I=0}{\overset{2<br><br>M-1}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>Q_{i,j<br><br>\left(t-1\right)}^{*}<br><br>Q_{i,k<br><br>\left(t-1\right)}=0,\mathrm{for}<br><br>\text{\hspace{1em}<br><br>}<br><br>j\ne <br><br>k$

where P_i,mt denotes a pilot symbol transmitted from an m^th transmit antenna of the BS on an i^th subcarrier at time t and Q_i,mt denotes a pilot symbol transmitted from an m^th transmit antenna of the RS on the i^th subcarrier at time t.

20. The relay system of claim 19, wherein when M is 2, each of the first and second pilot sequences is a sequence in the following pilot sequence set,

P_i1=[2 0 0 0 2 0 0 0 2 0 0 0 . . . ]
P_i2=[0 2 0 0 0 2 0 0 0 2 0 0 . . . ]
Q_i1=[0 0 2 0 0 0 2 0 0 0 2 0 . . . ]
Q_i2=[0 0 0 2 0 0 0 2 0 0 0 2 . . . ]
P_i1=[1 1 1 1 1 1 1 1 1 1 1 1 . . . ]
P_i2=[1 −

1 1 −

1 1 −

1 1 −

1 1 −

1 1 −

1 . . . ]
Q_i1=[1 −

1 −

1 1 1 −

1 −

1 1 1 −

1 −

1 1 . . . ]
Q_i2=[1 1 −

1 −

1 1 1 −

1 −

1 1 1 −

1 −

1 . . . ]

where P_i1 denotes a first pilot sequence transmitted on an i^th subcarrier from a first antenna of the BS, P_i2 denotes a first pilot sequence transmitted on the i^th subcarrier from a second antenna of the BS, Q_i1 denotes a second pilot sequence transmitted on the i^th subcarrier from a first antenna of the RS, and Q_i2 denotes a second pilot sequence transmitted on the i^th subcarrier from a second antenna of the RS.

21. The relay system of claim 10, wherein for at least two antennas in each of the BS and the RS, the first and second pilot sequences are at least one of cyclically shifted sequences and CAZAC sequences of a period determined by the number of the antennas.

22. The relay system of claim 10, further comprising the at least one MS for performing channel estimation using the second pilot sequence and receiving a signal from the RS using a result of the channel estimation.