1. A method of determining link cost for routing in an at least partially wireless multihop network, said method comprising the steps of:
estimating, for a wireless link between a pair of network nodes where at least one of the nodes is configured for operation with multiple antennas to provide for multiple channels, multi-channel characteristics between the nodes including an M\xd7N dimensional complex channel gain vector or matrix Hij, between node vi and node vj:
H
=
h
11
\u2026
h
1
\u2062
N
\u22ee
\u22f1
\u22ee
h
M
\u2062
\u2062
1
\u2026
h
MN
where hmn is a complex representation of the channel between transmit antenna n in a first one of said nodes and receive antenna m in a second one of said nodes, where at least one of N and M is greater than 1 to provide for multi-channel behavior; and
determining link cost for said wireless link based on the estimated multi-channel characteristics including said M\xd7N dimensional complex channel gain vector or matrix Hij, wherein the link cost is determined based on the inverse of the average rate according to:
\u0394Cij=1 rij,
where the average rate for a link from node vi to vj is determined based on the complex channel gain vector or matrix Hij of dimension M\xd7N, defined between node vi and node vj according to:
r
_
ij
=
B
\xb7
E
\u2061
(
log
2
\u2061
(
Det
\u2061
(
I
i
+
P
i
N
\xb7
\u03c3
\u2062
N
2
\xb7
H
ij
\xb7
H
ij
H
)
)
)
,
where B is the bandwidth, which may be neglected if only one common bandwidth is used in the whole system, E{ . . . } is an optional expectation value, Det{ . . . } is the determinant, Ii is the identity matrix of dimension M by M, Pi is the transmit power of node vi, \u03c3N2 is one or both of the noise level at node vj and average interference apart from receiver noise, and H is the Hermitian operator.
2. A method for link-cost based route determination in an at least partially wireless multihop network, said method comprising the steps of:
estimating, for a wireless link between a pair of network nodes where at least one of the nodes is configured for operation with multiple antennas to provide for multiple channels, multi-channel characteristics between the nodes including an M\xd7N dimensional complex channel gain vector or matrix Hij, between node vi and node vj:
H
=
h
11
\u22ef
h
1
\u2062
N
\u22ee
\u22f1
\u22ee
h
M
\u2062
1
\u22ef
h
MN
where hmn is a complex representation of the channel between transmit antenna n in a first one of said nodes and receive antenna m in a second one of said nodes, where at least one of N and M is greater than 1 to provide for multi-channel behavior; and
determining link cost for said wireless link based on the estimated multi-channel characteristics including said M\xd7N dimensional complex channel gain vector or matrix Hij, wherein the link cost is determined based on the inverse of the average rate according to:
\u0394Cij=1 rij,
where the average rate for a link from node vi to vj is determined based on the complex channel gain vector or matrix Hij of dimension M\xd7N, defined between node vi and node vj according to:
r
_
ij
=
B
\xb7
E
\u2061
(
log
2
\u2061
(
Det
\u2061
(
I
i
+
P
i
N
\xb7
\u03c3
\u2062
N
2
\xb7
H
ij
\xb7
H
ij
H
)
)
)
,
where B is the bandwidth, which may be neglected if only one common bandwidth is used in the whole system, E{ . . . } is an optional expectation value, Det{ . . . } is the determinant, Ii is the identity matrix of dimension M by M, Pi is the transmit power of node vi, \u03c3N2 is one or both of the noise level at node vj and average interference, and H is the Hermitian operator; and
performing route determination at least partly based on said determined link cost.
3. A method for link-cost based routing of data in an at least partially wireless multihop network, said method comprising the steps of:
estimating, for a wireless link between a pair of network nodes where at least one of the nodes is configured for operation with multiple antennas to provide for multiple channels, multi-channel characteristics between the nodes including an M\xd7N dimensional complex channel gain vector or matrix Hij, between node vi and node vj:
H
=
h
11
\u22ef
h
1
\u2062
N
\u22ee
\u22f1
\u22ee
h
M
\u2062
1
\u22ef
h
MN
where hmn is a complex representation of the channel between transmit antenna n in a first one of said nodes and receive antenna m in a second one of said nodes, where at least one of N and M is greater than 1 to provide for multi-channel behavior; and
determining link cost for said wireless link based on the estimated multi-channel characteristics including said M\xd7N dimensional complex channel gain vector or matrix Hij, wherein the link cost is determined based on the inverse of the average rate according to:
\u0394Cij=1 rij,
where the average rate for a link from node vi to vj is determined based on the complex channel gain vector or matrix Hij of dimension M\xd7N, defined between node vi and node vj according to:
r
_
ij
=
B
\xb7
E
\u2061
(
log
2
\u2061
(
Det
\u2061
(
I
i
+
P
i
N
\xb7
\u03c3
\u2062
N
2
\xb7
H
ij
\xb7
H
ij
H
)
)
)
,
where B is the bandwidth, which may be neglected if only one common bandwidth is used in the whole system, E{ . . . } is an optional expectation value, Det{ . . . } is the determinant, Ii is the identity matrix of dimension M by M, Pi is the transmit power of node vi, \u03c3N2 is one or both of the noise level at node vj and average interference, and H is the Hermitian operator;
performing route determination at least partly based on said determined link cost; and
forwarding data from a given node to at least a neighbor node on the path to a given destination node in accordance with said route determination.
4. The method of claim 1, wherein link cost is determined also based on knowledge of the multiple-antenna communication scheme used between the nodes.
5. The method of claim 4, wherein link cost is determined according to a function that is dependent on the multiple-antenna communication scheme.
6. The method of claim 5, further comprising the step of selecting multiple-antenna communication scheme from those schemes that are supported by both of the network nodes so as to optimize link cost.
7. The method of claim 1, wherein the average link rate is determined based on the expectation value of said M\xd7N dimensional complex channel gain vector or matrix Hij for a given transmit power Pi.
8. The method of claim 1, wherein said network is a fully wireless multihop network.
9. The method of claim 1, wherein said network is an ad-hoc multihop network.
10. The method of claim 1, wherein said pair of network nodes includes a mobile station and a base station, and handover between base stations in a cellular network is part of the routing process.
11. An arrangement for determining link cost for routing in an at least partially wireless multihop network, said arrangement comprising:
means for estimating, for a wireless link between a pair of network nodes where at least one of the nodes is configured for operation with multiple antennas to provide for multiple channels, multi-channel characteristics between the nodes including an M\xd7N dimensional complex channel gain vector or matrix Hij between node vi and node vj:
H
=
h
11
\u22ef
h
1
\u2062
N
\u22ee
\u22f1
\u22ee
h
M
\u2062
1
\u22ef
h
MN
where hmn is a complex representation of the channel between transmit antenna n in a first one of said nodes and receive antenna m in a second one of said nodes, where at least one of N and M is greater than 1 to provide for multi-channel behavior; and
means for determining link cost for said wireless link based on the estimated multi-channel characteristics including said M\xd7N dimensional complex channel gain vector or matrix Hij, wherein the link cost is determined based on the inverse of the average rate according to:
\u0394Cij=1 rij,
where the average rate for a link from node vi to vj is determined based on the complex channel gain vector or matrix Hij of dimension M\xd7N, defined between node vi and node vj according to:
r
_
ij
=
B
\xb7
E
\u2061
(
log
2
\u2061
(
Det
\u2061
(
I
i
+
P
i
N
\xb7
\u03c3
\u2062
N
2
\xb7
H
ij
\xb7
H
ij
H
)
)
)
,
where B is the bandwidth, which may be neglected if only one common bandwidth is used in the whole system, E{ . . . } is an optional expectation value, Det{ . . . } is the determinant, Ii is the identity matrix of dimension M by M, Pi is the transmit power of node vi, \u03c3N2 is one or both of the noise level at node vj and average interference, and H is the Hermitian operator.
12. An arrangement for link-cost based route determination in an at least partially wireless multihop network, said arrangement comprising:
means for estimating, for a wireless link between a pair of network nodes where at least one of the nodes is configured for operation with multiple antennas to provide for multiple channels, multi-channel characteristics between the nodes including an M\xd7N dimensional complex channel gain vector or matrix Hij, between node vi and node vj:
H
=
h
11
\u22ef
h
1
\u2062
N
\u22ee
\u22f1
\u22ee
h
M
\u2062
1
\u22ef
h
MN
where hmn is a complex representation of the channel between transmit antenna n in a first one of said nodes and receive antenna m in a second one of said nodes, where at least one of N and M is greater than 1 to provide for multi-channel behavior; and
means for determining link cost for said wireless link based on the estimated multi-channel characteristics including said M\xd7N dimensional complex channel gain vector or matrix Hij, wherein the link cost is determined based on the inverse of the average rate according to:
\u0394Cij=1 rij,
where the average rate for a link from node vi to vj is determined based on the complex channel gain vector or matrix Hij of dimension M\xd7N, defined between node vi and node vj according to:
r
_
ij
=
B
\xb7
E
\u2061
(
log
2
\u2061
(
Det
\u2061
(
I
i
+
P
i
N
\xb7
\u03c3
\u2062
N
2
\xb7
H
ij
\xb7
H
ij
H
)
)
)
,
where B is the bandwidth, which may be neglected if only one common bandwidth is used in the whole system, E{ . . . } is an optional expectation value, Det{ . . . } is the determinant, Ii is the identity matrix of dimension M by M, Pi is the transmit power of node vi, \u03c3N2 is one or both of the noise level at node vj and average interference, and H is the Hermitian operator; and
means for performing route determination at least partly based on said determined link cost.
13. An arrangement for link-cost based routing of data in an at least partially wireless multihop network, said arrangement comprising:
means for estimating, for a wireless link between a pair of network nodes where at least one of the nodes is configured for operation with multiple antennas to provide for multiple channels, multi-channel characteristics between the nodes including an M\xd7N dimensional complex channel gain vector or matrix Hij, between node vi and node vj:
H
=
h
11
\u22ef
h
1
\u2062
N
\u22ee
\u22f1
\u22ee
h
M
\u2062
1
\u22ef
h
MN
where hmn is a complex representation of the channel between transmit antenna n in a first one of said nodes and receive antenna m in a second one of said nodes, where at least one of N and M is greater than 1 to provide for multi-channel behavior; and
means for determining link cost for said wireless link based on the estimated multi-channel characteristics including said M\xd7N dimensional complex channel gain vector or matrix Hij, wherein the link cost is determined based on the inverse of the average rate according to:
\u0394Cij=1 rij,
where the average rate for a link from node vi to vj is determined based on the complex channel gain vector or matrix Hij of dimension M\xd7N, defined between node vi and node vj according to:
r
_
ij
=
B
\xb7
E
\u2061
(
log
2
\u2061
(
Det
\u2061
(
I
i
+
P
i
N
\xb7
\u03c3
\u2062
N
2
\xb7
H
ij
\xb7
H
ij
H
)
)
)
,
where B is the bandwidth, which may be neglected if only one common bandwidth is used in the whole system, E{ . . . } is an optional expectation value, Det{ . . . } is the determinant, Ii is the identity matrix of dimension M by M, Pi is the transmit power of node vi, \u03c3N2 is one or both of the noise level at node vj and average interference, and H is the Hermitian operator;
means for performing route determination at least partly based on said determined link cost; and
means for forwarding data from a given node to at least a neighbor node on the path to a given destination node in accordance with said route determination.
14. The arrangement of claim 11, wherein said determining means is operable for determining link cost also based on knowledge of the multiple-antenna communication scheme used between the nodes.
15. The arrangement of claim 14, wherein said determining means is operable for determining link cost according to a function that is dependent on the multiple-antenna communication scheme.
16. The arrangement of claim 15, further comprising means for selecting multiple-antenna communication scheme from those schemes that are supported by both of the network nodes so as to optimize link cost.
17. The arrangement of claim 11, wherein said determining means comprises means for determining the average link rate based on the expectation value of the M\xd7N dimensional complex channel gain vector or matrix Hij for a given transmit power Pi.
18. The arrangement of claim 11, wherein said network is a fully wireless multihop network.
19. The arrangement of claim 11, wherein said network is an ad-hoc multihop network.
20. The arrangement of claim 11, wherein said pair of network nodes includes a mobile station and a base station, and handover between base stations in a cellular network is part of the routing process.
21. The arrangement of claim 11, wherein said arrangement is implemented in at least one network node in the multihop network.
22. The arrangement of claim 12, wherein said means for performing route determination is operable for performing route determination also based on link cost for at least one further wireless or wired link in the multihop network.
23. A method for path selection from a mobile station to a mobility anchor point including selection among base stations in a cellular network, said mobile station being capable of communicating with said base stations via respective wireless links, said method comprising the steps of:
estimating, for each one of said wireless link, where at least one of the involved nodes is configured for operation with multiple antennas to provide for multiple channels, multi-channel characteristics between the nodes including an M\xd7N dimensional complex channel gain vector or matrix Hij, between node vi and node vj:
H
=
h
11
\u22ef
h
1
\u2062
N
\u22ee
\u22f1
\u22ee
h
M
\u2062
1
\u22ef
h
MN
where hmn is a complex representation of the channel between transmit antenna n in a first one of said nodes and receive antenna m in a second one of said nodes, where at least one of N and M is greater than 1 to provide for multi-channel behavior;
determining, for each one of said wireless links, link cost based on the estimated multi-channel characteristics including said M\xd7N dimensional complex channel gain vector or matrix Hij, wherein the link cost is determined based on the inverse of the average rate according to:
\u0394Cij=1 rij,
where the average rate for a link from node vi to vj is determined based on the complex channel gain vector or matrix Hij of dimension M\xd7N, defined between node vi and node vj according to:
r
_
ij
=
B
\xb7
E
\u2061
(
log
2
\u2061
(
Det
\u2061
(
I
i
+
P
i
N
\xb7
\u03c3
\u2062
N
2
\xb7
H
ij
\xb7
H
ij
H
)
)
)
,
where B is the bandwidth, which may be neglected if only one common bandwidth is used in the whole system, E{ . . . } is an optional expectation value, Det{ . . . } is the determinant, Ii is the identity matrix of dimension M by M, Pi is the transmit power of node vi, \u03c3N2 is one or both of the noise level at node vj and average interference, and H is the Hermitian operator; and
selecting an appropriate base station to use for mobile communication based on accumulated link cost along the respective path from said mobile station to said mobility anchor point.
24. An arrangement for path selection from a mobile station to a mobility anchor point including selection among base stations in a cellular network, said mobile station being capable of communicating with said base stations via respective wireless links, said arrangement comprising:
means for estimating, for each one of said wireless link, where at least one of the involved nodes is configured for operation with multiple antennas to provide for multiple channels, multi-channel characteristics between the nodes including an M\xd7N dimensional complex channel gain vector or matrix Hij, between node vi and node vj:
H
=
h
11
\u22ef
h
1
\u2062
N
\u22ee
\u22f1
\u22ee
h
M
\u2062
1
\u22ef
h
MN
where hmn is a complex representation of the channel between transmit antenna n in a first one of said nodes and receive antenna m in a second one of said nodes, where at least one of N and M is greater than 1 to provide for multi-channel behavior;
means for determining, for each one of said wireless links, link cost based on the estimated multi-channel characteristics including said M\xd7N dimensional complex channel gain vector or matrix Hij, wherein the link cost is determined based on the inverse of the average rate according to:
\u0394Cij=1 rij,
where the average rate for a link from node vi to vj is determined based on the complex channel gain vector or matrix Hij of dimension M\xd7N, defined between node vi and node vj according to:
r
_
ij
=
B
\xb7
E
\u2061
(
log
2
\u2061
(
Det
\u2061
(
I
i
+
P
i
N
\xb7
\u03c3
\u2062
N
2
\xb7
H
ij
\xb7
H
ij
H
)
)
)
,
where B is the bandwidth, which may be neglected if only one common bandwidth is used in the whole system, E{ . . . } is an optional expectation value, Det{ . . . } is the determinant, Ii is the identity matrix of dimension M by M, Pi is the transmit power of node Vi, \u03c3N2 is one or both of the noise level at node vj and average interference, and H is the Hermitian operator; and
means for selecting an appropriate base station to use for mobile communication based on accumulated link cost along the respective path from said mobile station to said mobility anchor point.
25. The method of claim 1, wherein the link cost is computed by assuming that power constrained waterfilling of the eigenchannels is performed.
26. The arrangement of claim 11, wherein said means for determining link cost is configured to compute the link cost by assuming that power constrained waterfilling of the eigenchannels is performed.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An eye refractive power measurement apparatus for measuring eye refractive power of an eye of an examinee, the apparatus comprising:
a measurement optical system for photo-receiving measurement light from a fundus via a ring-shaped aperture arranged at an approximately conjugate position with a pupil by using a photodetector;
changing means for changing a size of the ring-shaped aperture on a pupillary surface to a size different in both inside diameter and outside diameter; and
calculation means for calculating the eye refractive power based on a photo-receiving result obtained by the photodetector.
2. The eye refractive power measurement apparatus according to claim 1, wherein the changing means changes the size of the ring-shaped aperture on the pupillary surface based on the photo-receiving result obtained by the photodetector.
3. The eye refractive power measurement apparatus according to claim 1, further comprising pupil detecting means for detecting at least one of a pupil diameter and a pupil position of the eye,
wherein the changing means changes the size of the ring-shaped aperture on the pupillary surface based on a detection result obtained by the pupil detecting means.
4. The eye refractive power measurement apparatus according to claim 1, wherein the calculation means calculates the eye refractive power based on at least one of the respective photo-receiving results when the size of the ring-shaped aperture on the pupillary surface is changed.
5. The eye refractive power measurement apparatus according to claim 1, further comprising alignment detecting means for detecting an alignment state of the measurement optical system with the eye,
wherein the calculation means calculates corrected eye refractive power based on a detection result obtained by the alignment detecting means.
6. The eye refractive power measurement apparatus according to claim 1, wherein the measurement optical system projects the measurement light onto the fundus via a central pupillary portion, and photo-receives the measurement light reflected from the fundus via a peripheral pupillary portion and the ring-shaped aperture by using the photodetector.
7. The eye refractive power measurement apparatus according to claim 1, wherein the measurement optical system projects the measurement light onto the fundus via the ring-shaped aperture and a peripheral pupillary portion and photo-receives the measurement light reflected from the fundus via a central pupillary portion using the photodetector.