System and method for adjusting downlink channel quality index in a wireless communications system
View Patent ↗In accordance with an embodiment, a method of operating a controller in a wireless communication system includes receiving channel feedback information from a communications node, adjusting the channel feedback information based on a measurement of interference from neighboring controllers, adjusting transmit parameters of the controller using the adjusted channel feedback information, and transmitting to the communications node using the adjusted transmit parameters.
1. A method of operating a base station, the method comprising:
receiving channel feedback information from a communications device;
determining an interference adjustment factor according to
CQI
adj_nonQPSK
=
1
Interf_Adj
CQI
feedback
=
1
Interf
FFR
(
RB
)
/
Interf
noFFR
CQI
feedback
,
where CQI feedback is the channel feedback information, Interf_Adj is the interference adjustment factor, Interf FFR (RB) is wideband interference at the resource block when fractional frequency reuse is used, and Interf noFFR is wideband interference when fractional frequency reuse is not used;
adjusting the channel feedback information in accordance with the interference adjustment factor; and
adjusting transmission parameters of the base station using the adjusted channel feedback information.
2. The method of claim 1 , wherein the CQI comprises a channel quality index.
3. The method of claim 1 , wherein obtaining the path-loss information comprises receiving reference sequence received power (RSRP) information from the communications node, the RSRP information corresponding to measurements taken by the communications node of reference sequences transmitted by the one or more neighboring controllers.
4. The method of claim 3 , wherein obtaining the path-loss information comprises averaging multiple RSRP reports received from the communications node over a period of time.
5. The method of claim 3 , wherein the reference sequences are carried in downlink transmission frames sent by the one or more neighboring controllers.
6. The method of claim 1 , wherein obtaining the path-loss information comprises estimating a path-loss for each of the interference channels.
7. The method of claim 6 , wherein estimating the path-loss for each of the interference channels comprises estimating the path-loss in accordance with a cell topology of the controller and the one or more neighboring controllers.
8. The method of claim 1 , wherein adjusting the channel feedback information comprises:
adjusting the channel feedback information according to the interference adjustment factor when a difference between the power assigned for the resource block and the power assigned for the communications device is less than a threshold; and
adjusting the channel feedback information according to the interference adjustment factor and a signal power adjustment factor when the difference between the power assigned for the resource block and the power assigned for the communications device exceeds a threshold.
9. The method of claim 1 , further comprising:
determining whether phase-shift keying is used by the communications device;
adjusting the channel feedback information according to the interference adjustment factor and a signal power adjustment factor when phase-shift keying is used by the communications device; and
adjusting the channel feedback information according to the interference adjustment factor when phase-shift keying is not used by the communications device and the power assigned for the resource block is greater than the power assigned for the communications device.
10. The method of claim 9 , further comprising foregoing scheduling the resource block to the communications device when phase-shift keying is not used by the communications device and the power assigned for the resource block is less than the power assigned for the communications device.
11. The method of claim 10 , wherein foregoing scheduling the resource block comprises removing the communications device from a list of communication devices to be allocated resources for downlink transmissions.
12. The method of claim 9 , wherein adjusting the channel feedback information according to the interference adjustment factor comprises determining a value for CQI adj — nonQPSK according to:
CQI
adj_nonQPSK
=
1
Interf_Adj
CQI
feedback
=
1
Interf
FFR
(
RB
)
/
Interf
noFFR
CQI
feedback
,
and
wherein adjusting the channel feedback information according to the interference adjustment factor and the signal power adjustment factor comprises determining a value for CQI adj — QPSK according to:
CQI
adj_QPSK
=
Signal_Adj
Interf_Adj
CQI
feedback
=
P
s
(
RB
)
/
P
s
(
UE
)
Interf
FFR
(
RB
)
/
Interf
noFFR
CQI
feedback
,
where CQI feedback is the channel feedback information, Signal_Adj is the signal power adjustment factor, P s (RB) is the power assigned to the resource block, P s (UE) is the power assigned to the communications device, Interf_Adj is the interference adjustment factor, Interf FFR (RB) is wideband interference at the resource block when fractional frequency reuse is used, and Interf noFFR is wideband interference when fractional frequency reuse is not used.
13. A method of operating a base station, the method comprising:
receiving channel feedback information from a communications device;
determining an interference adjustment factor according to:
CQI
adj_QPSK
=
Signal_Adj
Interf_Adj
CQI
feedback
=
P
s
(
RB
)
/
P
s
(
UE
)
Interf
FFR
(
RB
)
/
Interf
noFFR
CQI
feedback
,
where CQI feedback is the channel feedback information, Signal_Adj is the signal power adjustment factor, Interf_Adj is the interference adjustment factor, P s (RB) is the power assigned to the resource block, P s (UE) is the power assigned to the communications device, Interf FFR (RB) is wideband interference at the resource block when fractional frequency reuse is used, and Interf noFFR is wideband interference when fractional frequency reuse is not used;
adjusting the channel feedback information in accordance with the interference adjustment factor; and
adjusting transmission parameters of the base station using the adjusted channel feedback information.