SPECTRAL SHARING WIRELESS SYSTEMS
Methods, systems, and devices for spectral sharing wireless systems, wherein multiple user devices share time and frequency resources for uplink and/or downlink transmissions, are described. One example method includes transmitting transmission symbols from the network station to at least one user device by processing through a first precoder and a pre-compensation stage, wherein the pre-compensation stage is selected to have the transmission symbols receivable at the at least one user device to appear as if the transmission symbols are processed by a second precoder different from the first precoder.
1 . A method of wireless communication, implemented by a network station in a wireless system comprising the network station and multiple user devices, comprising:
transmitting transmission symbols from the network station to at least one user device by processing through a first precoder and a pre-compensation stage, wherein the pre-compensation stage is selected to have the transmission symbols receivable at the at least one user device to appear as if the transmission symbols are processed by a second precoder different from the first precoder.
2 . The method of claim 1 , wherein the first precoder is a user device-specific precoder and the second precoder is a common precoder that is common to the multiple user devices.
3 . The method of claim 2 , wherein the user device-specific precoder is determined from the common precoder and covariance matrices for channels between the network station and the multiple user devices.
4 . The method of claim 3 , wherein, a covariance matrix R HH for a given channel, is calculated by modeling a response of the given channel as:
H
(
t
,
s
,
f
)
=
∑
i
=
1
N
r
α
i
·
e
2
π
j
f
τ
i
·
e
2
π
js
·
sin
(
θ
i
)
·
e
2
π
jtv
i
where α i , τ i , θ i and ν i represent complex gain, delay, angle of arrival and Doppler of ray i, respectively, and
where or N r represents a number of reflectors of the channel at a time t, space s and frequency f, and wherein the covariance matrix is calculated using a reflectors detection method or a maximum likelihood method.
5 . The method of claim 1 , wherein the second precoder is approximately an isotropic precoder.
6 . The method of claim 1 , wherein the transmission symbols are transmitted using dual polarization antennas.
7 . An apparatus for wireless communication, implemented at a network station in a wireless system comprising the network station and multiple user devices, the apparatus comprising one or more processors configured to cause the apparatus to implement a method, comprising:
transmitting transmission symbols from the network station to at least one user device by processing through a first precoder and a pre-compensation stage, wherein the pre-compensation stage is selected to have the transmission symbols receivable at the at least one user device to appear as if the transmission symbols are processed by a second precoder different from the first precoder.
8 . The apparatus of claim 7 , wherein the first precoder is a user device-specific precoder and the second precoder is a common precoder that is common to the multiple user devices.
9 . The apparatus of claim 8 , wherein the user device-specific precoder is determined from the common precoder and covariance matrices for channels between the network station and the multiple user devices.
10 . The apparatus of claim 9 , wherein, a covariance matrix R HH for a given channel, is calculated by modeling a response of the given channel as:
H
(
t
,
s
,
f
)
=
∑
i
=
1
N
r
α
i
·
e
2
π
j
f
τ
i
·
e
2
π
js
·
sin
(
θ
i
)
·
e
2
π
jtv
i
where α i , τ i , θ i and ν i represent the complex gain, delay, angle of arrival and Doppler of ray i, respectively, and
where or N r represents a number of reflectors of the channel at a time t, space s and frequency f, and wherein the covariance matrix is calculated using a reflectors detection method or a maximum likelihood method.
11 . The apparatus of claim 7 , wherein the second precoder is approximately an isotropic precoder.
12 . The apparatus of claim 7 , wherein the transmission symbols are transmitted using dual polarization antennas.