1. A magnetic disk apparatus, comprising:
a magnetic disk having a magnetic film formed on a substrate;
a spindle motor for rotating said magnetic disk;
a magnetic head for writingreading information onfrom said magnetic disk;
a supporting member for supporting said magnetic head;
a driving mechanism for moving said magnetic head to a predetermined position on said magnetic disk;
a magnetic writingreading circuit for enabling said magnetic head to writeread information onfrom said magnetic disk;
an interface for sendingreceiving signals for controlling said information tofrom another information processing device,
detection means for detecting whether or not the magnetic dish is being rotated; and
a latching mechanism to latch a movable part of said magnetic disk or said spindle motor on the basis of detection result of said detection means that the magnetic disk is not being rotated.
2. The magnetic disk apparatus according to claim 1,
wherein said detection means detects the rotation of the magnetic disk from at least one of a control signal sentreceived tofrom said information processing device via said interface and a voltage of power supplied from outside of the magnetic disk apparatus.
3. The magnetic disk apparatus according to claim 1,
wherein said latching mechanism comprises a small motor comprising a coil and a magnet and a member for coming into contact with said movable part to hold it.
4. The magnetic disk apparatus according to claim 1,
wherein said latching mechanism comprises an electromagnet.
5. The magnetic disk drive according to claim 1,
wherein said latching mechanism comprises a mechanism in which bimetal is used.
6. The magnetic disk apparatus according to claim 1,
wherein said latching mechanism comprises a mechanism in which a shape memory alloy is used.
7. A magnetic disk apparatus comprising:
a magnetic disk having a magnetic film formed on a substrate;
means for rotating said magnetic disk;
a magnetic head provided so as to face a surface of said magnetic disk;
means for positioning said magnetic head in a predetermined track on said magnetic disk;
a magnetic writingreading circuit for enabling said magnetic head to writeread information along said track;
an interface means for sendingreceiving the information and a signal to control the information tofrom an external information processing device, and
a latching mechanism to latch a movable part of the magnetic disk or the spindle motor, said latching mechanism unlatching said movable part when a specific command for readingwriting information fromonto said magnetic disk is issued from said information processing device and latching said movable part again after processing of said specific command is completed and the rotation of the magnetic disk is stopped.
8. The magnetic disk apparatus according to claim 7,
wherein said latching mechanism detects the rotation of the magnetic disk from a voltage of power supplied from outside of the magnetic disk apparatus.
9. The magnetic disk apparatus according to claim 7,
wherein said latching mechanism comprises a small motor comprising a coil and a magnet and a member for coming into contact with said movable part to hold it.
10. The magnetic disk apparatus according to claim 7,
wherein said latching mechanism comprises an electromagnet.
11. The magnetic disk drive according to claim 7,
wherein said latching mechanism comprises a mechanism in which bimetal is used.
12. The magnetic disk apparatus according to claim 7,
wherein said latching mechanism comprises a mechanism in which a shape memory alloy is used.
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. A method for dynamically optimizing data throughput at radio interfaces of a packet data cellular network, said interfaces comprising one or more types of modulations having different immunity from transmission errors when used for transmitting bursts of data, said data being packed-up in blocks between mobile stations and serving base station and vice versa, comprising the steps of:
obtaining for each available modulation at least one of an upgrade and a downgrade tabulated threshold of the Block Error Rate delimiting a range in which the available modulation outperforms other available modulations in terms of net data throughput;
averaging and comparing the Block Error Rate, substantially continuously, of the relevant temporary connection with the tabulated thresholds for selecting the proper modulation; combining each available modulation with two or more coding schemes thereby obtaining many modulation-and-coding schemes with different protection against transmission errors;
obtaining for each modulation and coding scheme at least one of a first upgrade and a first downgrade tabulated Block Error Rate threshold which is valid for low-diversity radio frequency channels, delimiting a range in which the modulation and coding scheme outperforms the other available modulation and coding schemes in terms of net data throughput, and considering as low-diversity a channel without frequency hopping and with low user mobility;
obtaining for each modulation and coding scheme at least one of a second upgrade and a second downgrade tabulated Block Error Rate threshold which is valid for high-diversity radio frequency channels, delimiting a range in which the modulation and coding scheme outperforms the other available modulation and coding schemes in terms of net data throughput, and considering as high-diversity a channel characterized by frequency hopping or high user mobility;
selecting either the first or the second tabulated thresholds according to diversity of the radio frequency channel which sustains a temporary connection; and
using the selected thresholds for discriminating a right modulation and coding scheme.
2. The method according to claim 1, wherein the step of discriminating a right modulation and coding scheme further comprises the steps of:
updating, at each new incoming block of data, an averaged value of Block Error Rate evaluated in correspondence of an actual modulation and coding scheme;
comparing the averaged Block Error Rate with the at least one of the upgrade and downgrade thresholds of the actual modulation and coding scheme; and
replacing the actual modulation and coding scheme with a modulation and coding scheme immediately less error protected when the averaged Block and Error Rate is lower than the upgrade threshold; or
replacing the actual modulation and coding scheme with the modulation and coding scheme immediately more error protected when the averaged Block and Error Rate is higher than the downgrade threshold.
3. The method according to claim 1, further comprising the steps of:
obtaining for each modulation and coding scheme at least one of a third upgrade and third downgrade tabulated Block Error Rate thresholds valid for both low-diversity channels and incremental redundancy active, and
delimiting a range in which the modulation and coding scheme outperforms the other available modulation and coding schemes in terms of net data throughput.
4. The method according to claim 3, further comprising the steps of:
obtaining for each modulation and coding scheme at least one of a fourth upgrade and downgrade tabulated Block Error Rate thresholds valid for both high-diversity channels and incremental redundancy active, and
delimiting a range in which the modulation and coding scheme outperforms the other available modulation and coding schemes in term of net data throughput.
5. The method according to claim 4, wherein a receiving entity performs the steps of:
temporarily storing errored data blocks in a memory buffer for joint decoding with new transmissions of original blocks according to an incremental redundancy technique; and
continuously checking a condition of buffer full and other causes making retransmission with incremental redundancy inapplicable, for building a status variable which measures an averaged status of the incremental redundancy.
6. The method according to claim 5, wherein for each modulation and coding scheme a linear interpolation is performed run-time between at least one of the first and third upgrade thresholds and between the first and third downgrade thresholds, using the status variable as interpolating factor for unbalancing the entity of the interpolation either towards third thresholds when incremental redundancy prevails, or towards first thresholds in a contrary case.
7. The method according to claim 5, wherein for each modulation and coding scheme a linear interpolation is performed run-time between at least one of the second and fourth upgrade thresholds and between the second and fourth downgrade thresholds, using the status variable as interpolating factor for unbalancing the entity of the interpolation either towards fourth thresholds when incremental redundancy prevails, or towards second thresholds in the contrary case.
8. The method according to claim 5, wherein the averaged status of the incremental redundancy is obtained by:
weighting both a preceding and an actual values of a variable,
taking value 1 when incremental redundancy is properly working, and value 0 for the contrary, and
using a digital filter having a pulse response exponentially decreasing with discrete time n spanning a data block period.
9. The method according to claim 7, wherein the linear interpolations comprise the following expressions:
UP\u2014thn=(1\u2212IR_statusn)\xd7BLERMCSx\u2192MCSy+IR_statusn\xd7BLERMCSx\u2014wIR\u2192MCSy\u2014wIR
DN\u2014thn=(1\u2212IR_statusn)\xd7BLERMCSx\u2192MCSz+IR_statusn\xd7BLERMCSx\u2014wIR\u2192MCSz\u2014wIR
wherein:
UP_thn and DN_thn are upgrade and downgrade thresholds, respectively, at an n-th block period;
BLERMCSx\u2192MCSy is an upgrade first (A) or second (B) tabulated threshold;
BLERMCSx\u2014wIR\u2192MCSy\u2014wIR is an upgrade third (C) or fourth (D) tabulated threshold;
BLERMCSx\u2192MCSz is a downgrade first (A) or second (B) tabulated threshold;
BLERMCSx\u2014wIR\u2192MCSz\u2014wIR is a downgrade third (C) or fourth (D) tabulated threshold.
10. The method according to claim 8, wherein the temporary connection is dedicated to transfer packet data from a selected mobile station to the base station, and said pulse response of the digital filter of the status variable is obtained according to the following function:
IR_statusn=f1(IR_statusn\u22121)+f2(IR_checkn)
wherein:
n is an iteration index spanning one block period; and
f1 and f2 are weight functions according to same laws as used in the Block Error Rate calculation.
11. The method according to claim 10, wherein the first and second weight functions comprise the following expressions:
f
1
\u2061
(
IR_status
n
–
1
)
=
(
1
–
\u03b2
\xb7
x
n
R
n
)
\xb7
IR_status
n
–
1
f
2
\u2061
(
IR_check
n
)
=
\u03b2
\xb7
x
n
R
n
\xb7
IR_check
n
wherein: Rn takes a formal expression as that used in the Block Error Rate calculation, while xn and \u03b2 are the same.
12. The method according to claim 1, wherein the averaged value of Block Error Rate is obtained by weighting both preceding values of Block Error Rate and actual decisions on errored blocks, using a digital filter having a pulse response exponentially decreasing with discrete time n spanning a block period.
13. The method according to claim 12, wherein the pulse response of the digital filter of Block Error Rate is obtained by summing two weight functions both accepting samples with a commanded modulation and coding scheme, a first one to weigh the preceding values of Block Error Rate and the second one to weigh the actual decisions on errored blocks.
14. The method according to claim 13, wherein the first and second weight functions have balanced weights, so that an arbitrary increasing of a weight of the first function also involves an equal decreasing of the weight of the second function, and vice versa.
15. The method according to claim 14, wherein the weight of the first and second weight functions are both equally varied in order to compensate a missing filtering effect of possible lacking blocks, in that making an outlined pulse response possible.
16. The method according to claim 15, wherein the first and second weights are carried out by making the first and second weight functions further depending on a reliability function which tracks an age of the received blocks.
17. the method according to claim 16, wherein the temporary connection is dedicated to transfer packet data from a selected mobile station to the base station, and the pulse response of Block Error Rate digital filter is obtained according to the function:
BLERn=f1(BLERn\u22121)+f2(sn)
wherein:
n is an iteration index spanning one block period;
sn=0 when a block at instant n has been correctly received;
sn=1 when a block at instant n has not been correctly received;
s
n
=
1
K
\u2062
\u2211
k
=
1
K
\u2062
s
n
,
k
when K blocks are received for a considered connection;
f1(BLERn\u22121) is the first weight function, taking values inside an interval 0-1; and
f2(sn) is the second weight function of the variable sn relative to a decision on the errored blocks, taking values inside the interval 0-1.
18. the method according to claim 16, wherein the temporary connection is dedicated to transfer packet data from the base station to a selected mobile station, and the pulse response of Block Error Rate digital filter is obtained according to the following function:
BLERk=f1(BLERk\u22121)+f2(sk)
wherein:
k is a reporting instant lasting m blocks;
s
k
=
Nack_blocks
Sent_blocks
Nack_blocks: number of badly received blocks among those sent with a present MCS;
Sent_blocks: number of blocks sent with a present MCS in a previous polling period:
f1(BLERk\u22121) is the first weight function, taking values inside an interval 0-1; and
f2 (sk) is the second weight function of the variable sk relative to the decision on the errored blocks, taking values inside the interval 0-1.
19. The method according to claim 17, wherein the first and second weight functions comprise the following expressions:
f
1
\u2061
(
BLER
n
–
1
)
=
(
1
–
\u03b2
\xb7
x
n
R
n
)
\xb7
BLER
n
–
1
f
2
\u2061
(
s
n
)
=
\u03b2
\xb7
x
n
R
n
\xb7
s
n
wherein:
xn is equal to 1 when \u201cat least\u201d one Radio Link Control (RLC) block for a considered connection with a commanded MCS is received at time instant n, otherwise is set to 0;
\u03b2=1TAVG is a forgetting factor and TAVG being a filtering period in multiples of a radio block; and
Rn=(1\u2212\u03b2)\xb7Rn\u22121+\u03b2\xb7xn; R\u22121=0 is said reliability function.
20. The method according to claim 18, wherein the first and second weight functions comprise the following expressions:
f
1
\u2061
(
BLER
k
–
1
)
=
(
1
–
\u03b2
R
k
)
\xb7
BLER
k
–
1
f
2
\u2061
(
s
k
)
=
\u03b2
R
k
\xb7
s
k
wherein:
\u03b2=1TAVG is a forgetting factor and TAVG being a filtering period in multiples of a radio block; and
Rk=(1\u2212\u03b2)m\xb7Rk\u22121+\u03b2; R\u22121=0 is said reliability function.
21. The method according to claim 20, wherein the temporary connection is dedicated to transfer packet data from the base station to a selected mobile station, and the pulse response of the status variable digital filter is obtained according to the following function:
IR_statusk=f1(IR_statusk\u22121)+f2 (IR_checkk)
wherein:
k is a reporting instant lasting m blocks;
f1 and f2 are weight functions following the same laws as used in the Block Error Rate calculation.
22. The method according to claim 21, wherein the first and second weight functions comprise the following expressions:
f
1
\u2061
(
IR_status
k
–
1
)
=
(
1
–
\u03b2
R
k
)
\xb7
IR_check
k
–
1
f
2
\u2061
(
IR_check
k
)
=
\u03b2
R
k
\xb7
IR_check
k
.
23. The method according to claim 1, wherein a modified power control works in parallel with the modulation and coding scheme switching link adaptation and the modified power control includes the following steps:
off-line calculation of the expression:
TPxTS=TPNTS,
wherein: TPxTS is a Peak Throughput per timeslot; TP is a Peak Throughput derived from a Quality of Service Class of the connection, and NTS is a minimum between a number of allocable timeslots and a number of timeslots that can be handled by the mobile station due to its multislot class;
off-line mapping of the calculated TPxTS on a simulated curve depicting a maximum achievable net throughput in function of values of Carrier versus Interference CI, and obtaining from the curve a target CItarget value; and
exploiting the CItarget for all duration of the ongoing connection as a goal to be maintained by the network exploiting the Power and Interference measures at a receiver side.