Down-link transmission scheduling in CDMA data networks

• US 6,763,009 B1
• Filed: 12/03/1999
• Issued: 07/13/2004
• Est. Priority Date: 12/03/1999
• Status: Expired due to Term

• Current Assignee: RPX Corporation
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Bedekar, Anand S., Whiting, Philip A., Ramanan, Kavita, Yeh, Edmund M., Borst, Simon C.
• Primary Examiner(s): WASHINGTON, ERIKA ALISE
• Application Number:
  US09/454,039
• Time in Patent Office: 1,684 Days
• Field of Search: 370/335, 370/328, 370/342, 370/350, 370/318, 370/320, 370/321, 370/322, 370/326, 455/450, 455/453, 455/509, 455/511, 455/515, 455/516, 455/522
• US Class Current: 370/335
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04J 13/16 Code allocation
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A base station of a code division, multiple access (CDMA) telecommunications system employs scheduling of data transmission signals to corresponding user transceivers in down-link channels of a data network. One or more user transceivers may be in communication with a base station within a cell, and each user may have a minimum data rate requirement. In accordance with the present invention, the scheduling of user data transmission follows the constraints that 1) each base station transmits to user transceivers one at a time, and 2) the base station uses full available power for the down-link channel when transmitting (for data networks only). Given a data network of users, the method of scheduling and data rates may be modeled in accordance with a linear programming problem optimized according to a predefined criterion. In addition, the present method may be employed in a hybrid CDMA/time-share system to reduce power of data channels in communication with user transceivers near the base station. A continuum of rates may be achieved based on the system signal to interference ratio (S/I). The error rate requirement of a user'"'"'s down-link channel may be met provided the S/I of the channel is greater than a predetermined threshold value.

Claims

1. A method of intra-cell scheduling of transmission by a base station of one or more spread data signals to corresponding users in a cell comprising the steps of:

(a) allocating to each user of a first set of users one of a set of disjoint time intervals, and to each user of a second set of users a common time interval;

(b) defining a duty cycle as the relative maximum duration of time between successive time intervals of a user for two enabled transmissions of the corresponding spread data signal by the base station; and

(c) transmitting, by the base station, each spread data signal to the corresponding user during the allocated time interval, wherein each time interval of the duty cycle is non-overlapping and the base station transmits a spread data signal to one user at a time during the duty cycle.

2. The invention as recited in claim 1, wherein for step (c) the corresponding spread user signals for the second set of users are transmitted concurrently during the common time interval.

3. The invention as recited in claim 1, wherein each user is assigned to either the first or second set of users based on a set of spreading constraints.

4. The invention as recited in claim 1, wherein step (c) further includes the step of 1) transmitting at a transmit power level to each corresponding spread data signal of the first set of users, wherein the transmit power level is near a relative maximum transmit power of the base station.

5. A method of intra-cell scheduling of transmission by a base station of one or more spread data signals to one or more corresponding users in a cell, the method comprising:

(a) allocating to each of the one or more users a recurrent time interval during which transmission of each spread data signal from the base station to the corresponding user is enabled;

(b) before the allocating step, solving a linear problem that characterizes the cell, the linear problem having a set of constraints for optimization of throughput, to determine the recurrent time interval for each of said users; and

(c) after the allocating step, transmitting each of said one or more spread data signals from the base station to the corresponding user during an allocated time interval that does not overlap the time interval allocated to any other of said one or more users, such that a transmission is made to one user at a time, wherein a transmit power of each of said one or more spread data signals is near a relative maximum transmit power of the base station.

6. The invention as recited in claim 5, wherein the time intervals and transmit powers of the one or more spread data signals are allocated based on predetermined minimum average rates for corresponding users in the cell.

7. The invention as recited in claim 5, wherein the time intervals and transmit powers of the one or more spread data signals are determined for corresponding users in the cell in accordance with an optimization criterion based on relative throughput.

8. The invention as recited in claim 5, wherein the time intervals and transmit powers of the one or more spread data signals are determined using received signal-to-interference noise values measured by corresponding users in the cell.

9. The invention as recited in claim 5, wherein, for step (a), each user of a first set of users is allocated one of a set of disjoint time intervals, and each user of a second set of users is allocated a common time interval.

10. The invention as recited in claim 9, wherein for step (c) the corresponding spread user signals for the second set of users are transmitted concurrently during the common time interval.

11. The invention as recited in claim 9, wherein each user is assigned to either the first or second set of users based on a set of spreading constraints.

12. The invention as recited in claim 9, wherein:

step (c) comprises transmitting each corresponding spread data signal of the first set of users at a transmit power level; and

said transmit power level is near the relative maximum transmit power of the base station.

13. A method of intra-cell scheduling of transmission by a base station of one or more spread data signals to one or more corresponding users in a cell, the method comprising:

(a) allocating to each of the one or more users a recurrent time interval during which transmission of each spread data signal from the base station to the corresponding user is enabled;

(b) before the allocating step, solving a linear programming problem that characterizes the cell, thereby to determine the recurrent time interval for each of said users;

(c) after the allocating step, transmitting each of said one or more spread data signals from the base station to the corresponding user during an allocated time interval that does not overlap the time interval allocated to any other of said one or more users, such that a transmission is made to one user at a time; and

(d) transmitting, by the base station, one or more spread signals to one or more corresponding delay-intolerant users in the cell, wherein the base station transmits each spread signal to the corresponding delay-intolerant user during a corresponding time period that overlaps one or more time intervals and step (d) comprises the steps of;

d1) allocating a transmit power to each spread data signal, the transmit power defined as the difference between a relative maximum transmit power of the base station and a total transmit power allocated to the one or more spread signals of the delay-intolerant users, and

d2) transmitting each spread data signal with the corresponding transmit power during the time interval.

14. The invention as recited in claim 13, wherein, for step (d), each spread signal of a delay-intolerant user is either a voice or a voiceband data spread signal.

15. A method of intra-cell scheduling of transmission by a base station of one or more spread data signals to one or more corresponding users in a cell, the method comprising:

(a) allocating to each of the one or more users a recurrent time interval during which transmission of each spread data signal from the base station to the corresponding user is enabled, wherein step (a) comprises the steps of;

a1) allocating to each user of a first set of users one of a set of disjoint time intervals, and

a2) allocating to each user of a second set of users a common time interval;

(b) before the allocating step, solving a linear programming problem that characterizes the cell, thereby to determine the recurrent time interval for each of said users; and

(c) after the allocating step, transmitting each of said one or more spread data signals from the base station to the corresponding user during an allocated time interval that does not overlap the time interval allocated to any other of said one or more users, such that a transmission is made to one user at a time, wherein step (c) comprises the steps of;

c1) allocating a transmit power to each spread data signal, and

c2) transmitting each spread data signal with the corresponding transmit power during the time interval, wherein the transmit power level of the first set of users is near a relative maximum transmit power of the base station.

16. Apparatus for intra-cell scheduling of transmission by a base station of one or more spread data signals to corresponding users in a cell comprising:

a control module for;

(1) allocating to each of the one or more users a recurrent time interval during which transmission of each spread data signal from the base station to the corresponding user is enabled, and

(2) before the allocating step, solving a linear problem that characterizes the cell, the linear problem having a set of constraints for optimization of throughput, to determine the recurrent time interval for each of said users; and

a transmit module for transmitting each of said one or more spread data signals from the base station to the corresponding user during an allocated time interval that does not overlap the time interval allocated to any other of said one or more users, such that a transmission is made to one user at a time,

wherein a transmit power of each of said one or more spread data signals is near a relative maximum transmit power of the base station.

17. The invention as recited in claim 16, wherein the time intervals and transmit powers of the one or more spread data signals are allocated based on predetermined minimum average rates for corresponding users in the cell.

18. The invention as recited in claim 16, wherein the time intervals and transmit powers of the one or more spread data signals are determined for corresponding users in the cell in accordance with an optimization criteria based on relative throughput.

19. The invention as recited in claim 16, wherein the time intervals and transmit powers of the one or more spread data signals are determined using received signal-to-interference noise values measured by corresponding users in the cell.

20. The invention as recited in claim 16, wherein each user of a first set of users is allocated one of a set of disjoint time intervals, and each user of a second set of users is allocated a common time interval.

21. The invention as recited in claim 20, wherein the corresponding spread user signals for the second set of users are transmitted concurrently during the common time interval.

22. The invention as recited in claim 20, wherein each user is assigned to either the first or second set of users based on a set of spreading constraints.

23. The invention as recited in claim 20, wherein the transmit module transmits at a transmit power level to each corresponding spread data signal of the first set of users, wherein the transmit power level is near the relative maximum transmit power of the base station.

24. Apparatus for intra-cell scheduling of transmission by a base station of one or more spread data signals to corresponding users in a cell comprising:

a control module for;

(1) allocating to each of the one or more users a recurrent time interval during which transmission of each spread data signal from the base station to the corresponding user is enabled, and

(2) before the allocating step, solving a linear programming problem that characterizes the cell, thereby to determine the recurrent time interval for each of said users; and

a transmit module for transmitting each of said one or more spread data signals from the base station to the corresponding user during an allocated time interval that does not overlap the time interval allocated to any other of said one or more users, such that a transmission is made to one user at a time,

wherein the transmit module further transmits one or more spread signals to one or more corresponding delay-intolerant users in the cell during a duty cycle such that each corresponding spread signal is transmitted during a corresponding time period that overlaps one or more time intervals, and

wherein the control module allocates a transmit power to each spread data signal, the transmit power defined as the difference between a relative maximum transmit power of the base station and a total transmit power allocated to the one or more spread signals of delay-intolerant users; and

the transmit module transmits each spread data signal with the corresponding transmit power during the time interval.

25. The invention as recited in claim 24, wherein each spread signal of a delay-intolerant user is either a voice or a voiceband data spread signal.

26. Apparatus for intra-cell scheduling of transmission by a base station of one or more spread data signals to corresponding users in a cell comprising:

a control module for;

(1) allocating to each of the one or more users a recurrent time interval during which transmission of each spread data signal from the base station to the corresponding user is enabled, wherein each user of a first set of users is allocated one of a set of disjoint time intervals, and each user of a second set of users is allocated a common time interval, and

(2) before the allocating step, solving a linear programming problem that characterizes the cell, thereby to determine the recurrent time interval for each of said users,

wherein the control module allocates a transmit power to each spread data signal, and the transmit module transmits each spread data signal with the corresponding transmit power during the time interval; and

a transmit module for transmitting each of said one or more spread data signals from the base station to the corresponding user during an allocated time interval that does not overlap the time interval allocated to any other of said one or more users, such that a transmission is made to one user at a time,

wherein the transmit module transmits each corresponding spread data signal to the first set of users at a transmit power level, wherein the transmit power level is near a relative maximum transmit power of the base station.

27. A computer-readable medium having stored thereon a plurality of instructions, the plurality of instructions including instructions which, when executed by a processor, cause the processor to implement a method for of intra-cell scheduling of transmission by a base station of one or more spread data signals to corresponding users in a cell, the method comprising the steps of:

(a) allocating to each of the one or more users a recurrent time interval during which transmission of each spread data signal from the base station to the corresponding user is enabled;

(b) before the allocating step, solving a linear problem that characterizes the cell, the linear problem having a set of constraints for optimization of throughput, to determine the recurrent time interval for each of said users; and

(c) after the allocating step, transmitting each of said one or more spread data signals from the base station to the corresponding user during an allocated time interval that does not overlap the time interval allocated to any other of said one or more users, such that a transmission is made to one user at a time, wherein a transmit power of each of said one or more spread data signals is near a relative maximum transmit power of the base station.