Method and apparatus to vary power level of training signal
Briefly, a method to transmit over an uplink channel a training signal having a power level which varies according to a parameter related to downlink channel characteristics is provided. Communication system that includes communication devices to transmit and receive the training signal is further provided.
1. A method of assigning power levels to Orthogonal Frequency-Division Multiple Access (OFDMA) training signals comprising:
receiving, over a downlink, a message including a transmit method value, wherein the transmit method value indicates an interference dependent power scheme;
determining a transmission power level P(j) of each uplink OFDM training signal (j) according to
P
(
j
)
=
Tx
Power
+
10
log
10
(
1
T
n
min
i
σ
d
2
(
i
)
σ
d
2
(
j
)
)
,
wherein TxPower is a sum of transmit power per OFDMA symbol, T n is a number of training signals and σ d 2 (j) is the interference level measured at the vicinity of the j-th training signal;
decreasing the transmission power level of each uplink OFDMA training signal whose frequency is in a near vicinity of a frequency of an interferer signal according to the interference level of the interferer signal; and
transmitting the OFDM training signals over the uplink according to the interference dependent power scheme.
2. The method of claim 1 , wherein transmitting comprises:
transmitting at least one OFDMA training signal of the OFDMA training signals to provide a function of an interference level of a downlink channel.
3. The method of claim 1 , comprising:
transmitting a message over an uplink, wherein the message includes a value for calculating a characteristic of first and second downlink channels.
4. The method of claim 3 , wherein transmitting the message comprises transmitting the message including a signal to interference and noise ratio.
5. The method of claim 2 , comprising:
transmitting each OFDMA training signal at a power level inversely proportional to an interference level of a frequency in the vicinity of a downlink OFDMA training signal frequency, wherein a sum of power levels of all OFDMA training signals is not exceeding a desired average power level.
6. A wireless communication device comprising:
a receiver to receive, over a downlink, a message including a transmit method value, wherein the transmit method value indicates an interference dependent power scheme;
an estimator to estimate an interference power level of each Orthogonal Frequency-Division Multiple Access (OFDMA) training signal received over the downlink;
a power level controller to determine a transmission power p(j) of each uplink OFDM training signal (j) according to
P
(
j
)
=
Tx
Power
+
10
log
10
(
1
T
n
min
i
σ
d
2
(
i
)
σ
d
2
(
j
)
)
,
wherein TxPower is a sum of transmit power per OFDMA symbol, T n is a number of training signals and σ d 2 (j) is the interference level measured at the vicinity of the j-th training signal and said power level controller is able to decrease the transmission power level of each uplink OFDMA training signal whose frequency is in a near vicinity of a frequency of an interferer signal according to the interference level of the interferer signal; and
a transmitter to transmit the uplink OFDMA training signals according to the interference dependent power scheme.
7. The wireless communication device of claim 6 , wherein the transmitter is able to transmit each uplink OFDMA training signal at a power level inversely proportional to an interference level of a frequency in a vicinity in frequency of a downlink OFDMA training signal frequency and wherein a sum of power levels of the all uplink OFDMA training signals is not exceeding a desired average power level.
8. The wireless communication device of claim 6 , wherein the transmitter is able to transmit a message including a value of a characteristic of the downlink channel over an uplink.
9. The wireless communication device of claim 8 , wherein said characteristic is a signal to interference and noise ratio.
10. The wireless communication device of claim 6 , wherein the transmitter is able to transmit the uplink OFDMA training signal in a time division duplex system.
11. The wireless communication device of claim 6 , wherein the message includes an instruction to transmit uplink OFDMA training signals according to a fixed power scheme.
12. The method of claim 1 , comprising:
transmitting said message over an uplink, wherein the message includes an instruction to transmit uplink OFDMA training signals according to a fixed power scheme.