Rate control device and method for CDMA communication system

• US 6,700,881 B1
• Filed: 03/01/1999
• Issued: 03/02/2004
• Est. Priority Date: 03/02/1998
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Yoon, Soon-Young, Kim, Young-Ky, Ahn, Jae-Min, Kong, Seung-Hyun
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): Hyun, Soon-Dong
• Application Number:
  US09/260,213
• Time in Patent Office: 1,828 Days
• Field of Search: 370/335, 370/342, 370/332, 370/333, 370/252, 370/248, 370/441
• US Class Current: 370/335
• CPC Class Codes: H04B 7/264 for data rate control
• CPC Class Codes: H04B 7/2646 for broadband transmission
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0068 by puncturing
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence

Abstract

A traffic channel transmission device for a CDMA communication system using a plurality of coding rates and orthogonal codes, determines a present channel condition and adaptively selects a coding rate and an orthogonal code according to the determination. In the device, a channel receiver receives a channel signal and a controller analyzes the received signal to decide an environment of a channel in service and generates a coding rate select signal and orthogonal code information according to the decision result. A channel transmitter includes a channel encoder for encoding transmission data at a coding rate selected according to the coding rate select signal and an orthogonal modulator for generating an orthogonal code according to the orthogonal code information to spread the encoded data with the generated orthogonal code, whereby the channel transmitter adaptively encodes and spreads the transmission data according to the channel environment. The orthogonal code information includes a number and a length of the orthogonal code.

Claims

1. A channel communication apparatus for a wireless communication system comprising:

a channel receiver for receiving a channel signal;

a controller for analyzing the received channel signal to assess a channel environment, said assessment being used by said channel receiver to generate a coding rate select signal and orthogonal code information; and

a channel transmitter including;

a channel encoder for adaptively encoding transmission data at a coding rate selected according to the coding rate select signal, and an orthogonal modulator for generating an orthogonal code according to the orthogonal code information to spread the encoded transmission data with the generated orthogonal code;

wherein said controller performs said channel assessment by;

(i.) measuring at least one of a receiving power, interference, a bit error rate (BER) and a signal-to-noise ratio (SNR) from the received channel signal,

(ii.) comparing the measured values with corresponding upper threshold values to generate the coding rate select signal for decreasing the coding rate and the orthogonal code information by reducing a length of the orthogonal code when the measured values exceed the upper threshold values, and

(iii.) comparing the measured values with corresponding lower threshold values to generate the coding rate select signal for increasing the coding rate and the orthogonal code information by increasing the length of the orthogonal code when the measured values are below the lower threshold values.

2. The channel communication apparatus as claimed in claim 1, wherein said channel transmitter further comprises:

at least two channel encoders having different coding rates, for encoding an input transmission signal at a corresponding coding rate;

at least two interleavers for interleaving the corresponding encoded data by a frame unit;

selectors for selectively connecting the input transmission signal to the channel encoders according to the coding rate select signal and selectively outputting an output of the corresponding interleaver;

an orthogonal modulator for generating the orthogonal code corresponding to the orthogonal code information and spreading the encoded data output from the selected interleaver with the generated orthogonal code; and

a pseudo-random noise (PN) spreader for PN spreading the orthogonal spread signal.

3. The channel communication device as claimed in claim 2, wherein said orthogonal code information includes a number and a length of the orthogonal code.

4. The channel communication apparatus as claimed in claim 1, wherein said channel receiver further comprises:

a PN despreader for PN despreading the received signal;

an orthogonal demodulator for generating an orthogonal code corresponding to the orthogonal code information and orthogonally despreading the PN despread signal;

at least two deinterleavers for deinterleaving the orthogonally despread signal;

at least two channel encoders having different coding rates, for encoding the deinterleaved signal at the corresponding encoding rate; and

channel decoders for selectively connecting the orthogonally despread signal to the corresponding deinterleaver according to the coding rate select signal and selectively outputting an output of the channel encoder having the corresponding coding rate.

5. A channel communication apparatus for a wireless communication system using multiple carriers, comprising:

a channel receiver for receiving a channel signal;

a controller for analyzing the received channel signal to assess a channel environment, said assessment being used by said channel receiver to generate a coding rate select signal and orthogonal code information; and

a channel transmitter including;

a channel encoder for adaptively encoding transmission data at a coding rate selected according to the coding rate select signal, and an orthogonal modulator for generating an orthogonal code according to the orthogonal code information to spread the encoded transmission data with the generated orthogonal code;

wherein said controller performs said channel assessment by;

(i.) measuring at least one of a receiving power, interference, a bit error rate (BER) and a signal-to-noise ratio (SNR) from the received channel signal,

(ii.) comparing the measured values with corresponding upper threshold values to generate the coding rate select signal for decreasing the coding rate and the orthogonal code information by reducing a length of the orthogonal code when the measured values exceed the upper threshold values, and

(iii.) comparing the measure values with corresponding lower threshold values to generate the coding rate select signal for increasing the coding rate and the orthogonal code information by increasing the length of the orthogonal code when the measured values are below the lower threshold values.

6. The channel communication device as claimed in claim 5, wherein said channel transmitter comprises:

at least two channel encoders each having different coding rates, for encoding an input transmission signal at the corresponding coding rate;

interleavers for interleaving the encoded data output from the respective channel encoders, respectively;

selectors for selectively connecting the input transmission signal to the channel encoder having the corresponding coding rate according to the coding rate select signal and selectively outputting an output of the corresponding interleaver;

a demultiplexer for demultiplexing the encoded data output from the selectors to the respective carriers;

orthogonal modulators for generating the orthogonal code corresponding to the orthogonal code information and spreading the encoded data output from the demultiplexer with the generated orthogonal code; and

transmitters for PN spreading the orthogonal spread signals and transmitting the PN spread signals by carrying them on the corresponding carriers, respectively.

7. The channel communication device as claimed in claim 6, wherein said orthogonal code information includes a number and a length of the orthogonal code.

8. The channel communication device as claimed in claim 6, wherein said demultiplexer uniformly distributes the encoded data to the respective carriers.

9. The channel communication device as claimed in claim 5, wherein said channel receiver comprises:

PN despreaders for frequency shifting the received multicarrier signal using the corresponding carriers and PN despreading the frequency-shifted signals;

orthogonal demodulators for generating orthogonal codes corresponding to the orthogonal code information and despreading the PN despread signals with the corresponding orthogonal codes;

a demultiplexer for demultiplexing outputs of the orthogonal demodulators;

deinterleavers in the same number as that of the coding rates, for deinterleaving the despread signals;

at least two channel encoders each having different coding rates, for encoding the deinterleaved signal at the corresponding encoding rate; and

channel decoders for selectively connecting the orthogonally despread signal to the corresponding deinterleaver according to the coding rate select signal and selectively outputting an output of the channel encoder having the corresponding coding rate.

10. A channel communication method for a wireless communication system, comprising the steps of:

(i) analyzing an environment of a channel in service, and selecting a coding rate and orthogonal code when the channel environment satisfies a rate change condition;

(ii) generating a message including the selected coding rate and the orthogonal code;

(iii) sending the message to a mobile station; and

(iv) upon reception of a response message from the mobile station responsive to said message;

(v) switching from a presently selected coding rate and presently selected orthogonal code to the selected coding rate and orthogonal code in a channel transmitter;

wherein said step of selecting a coding rate comprises the steps of;

examining a call condition associated with the mobile station to determine whether the rate change condition is satisfied;

when a first rate change condition is satisfied, selecting a coding rate lower than a present coding rate of the mobile station and selecting an orthogonal code having a length corresponding to the selected coding rate; and

when a second rate change condition is satisfied, selecting a coding rate higher than a present coding rate of the mobile station and selecting an orthogonal code having a length corresponding to the selected coding rate.

11. The channel communication method as claimed in claim 10, wherein the first rate change condition is satisfied when a transmission power to the mobile station is higher than an average transmission power of all mobile stations presently in service and orthogonal codes corresponding to the selected coding rate are available.

12. The channel communication method as claimed in claim 11, wherein said average transmission power is obtained by subtracting a power margin from a maximum transmission power of the base station, and dividing the result by the number of mobile stations presently in service.

13. The channel communication method as claimed in claim 10, wherein said step of selecting an orthogonal code comprises the steps of:

selecting an orthogonal code length corresponding to the selected coding rate, and writing unused orthogonal codes having the selected length in a search list;

examining a correlation between the orthogonal codes in the search list and orthogonal codes longer than the orthogonal codes in the search list and deleting those orthogonal codes from the search list not satisfying orthogonality therebetween;

determining whether complementary orthogonal codes of those undeleted orthogonal codes from said search list in use;

selecting one of the orthogonal codes from said list whose complementary orthogonal code is in use;

examining a correlation between the orthogonal codes in the search list and orthogonal codes shorter than the orthogonal codes in the search list and deleting the orthogonal codes not unsatisfying the orthogonality therebetween, when there is no orthogonal code whose complementary orthogonal code is in use; and

selecting one of the orthogonal codes remaining in the search list after deletion.

14. The channel communication method as claimed in claim 10, wherein the first rate change condition is satisfied when a transmission power to the mobile station is higher than an average transmission power of all mobile stations presently in service, orthogonal codes corresponding to the selected coding rate are available, a receiving strength of a reverse link is lower than a reference strength value, and a signal-to-noise ratio of the reverse link is lower than a reference signal-to-noise ratio.

15. The channel communication method as claimed in claim 10, wherein the second rate change condition is satisfied when a transmission power to the corresponding mobile station is lower than a reference average transmission power to other mobile stations.

16. The channel communication method as claimed in claim 10, wherein the second rate change condition is satisfied when a transmission power to the corresponding mobile station is lower than a reference average transmission power to other mobile stations, a receiving strength of a reverse link is higher than a reference strength value, and a signal-to-noise ratio of the reverse link is higher than a reference signal-to-noise ratio.

17. A channel communication method for a wireless communication system, comprising the steps of:

upon reception of a rate change request message from a mobile station, selecting a coding rate and orthogonal code according to the rate change request message and determining whether there exist available orthogonal codes corresponding to the selected coding rate;

generating a response message Including information about the selected coding rate and orthogonal code and sending the generated response message to the mobile station initiating said rate change request message; and

switching a present coding rate and orthogonal code of a channel transmitter to the selected coding rate and orthogonal code;

wherein said step of selecting a coding rate comprises the steps of;

examining a call condition with the mobile station to determine whether a rate change condition is satisfied;

when a first rate change condition is satisfied, selecting a coding rate lower than a present coding rate of the mobile station and selecting an orthogonal code having a length corresponding to the selected coding rate; and

when a second rate change condition is satisfied, selecting a coding rate higher than a present coding rate of the mobile station and selecting an orthogonal code having a length corresponding to the selected coding rate.

18. The channel communication method as claimed in claim 17, wherein the first rate change condition is satisfied when a transmission power to the mobile station is higher than an average transmission power of all mobile stations presently in service, and orthogonal codes corresponding to the selected coding rate are available.

19. The channel communication method as claimed in claim 18, wherein said average transmission power is obtained by subtracting a power margin from a maximum transmission power of the base station and then dividing the result by the number of the mobile stations presently in service.

20. The channel communication method as claimed in claim 17, wherein said orthogonal code selection step comprises the steps of:

selecting an orthogonal code length corresponding to the selected coding rate, and writing unused orthogonal codes having the selected length in a search list;

examining a correlation between the orthogonal codes in the search list and orthogonal codes longer than the orthogonal codes in the search list and deleting those orthogonal codes from said search list not satisfying orthogonality therebetween;

determining whether complementary orthogonal codes of those undeleted orthogonal codes from said search list are in use;

selecting one of the orthogonal codes from said list whose complementary orthogonal codes is in use;

examining a correlation between the orthogonal codes in the search list and orthogonal codes shorter than the orthogonal codes in the search list and deleting the orthogonal codes not unsatisfying the orthogonality therebetween, when there is no orthogonal code whose complementary orthogonal code is in use; and

selecting one of the orthogonal codes remaining in the search list after deletion.

21. The channel communication method as claimed in claim 17, wherein the first rate change condition is satisfied when a transmission power to the mobile station is higher than an average transmission power of all mobile stations presently in service, orthogonal codes corresponding to the selected coding rate are available, a receiving strength of a reverse link is lower than a reference strength value, and a signal-to-noise ratio of the reverse link is lower than a reference signal-to-noise ratio.

22. The channel communication method as claimed in claim 17, wherein the second rate change condition is satisfied when a transmission power to the corresponding mobile station is lower than a reference average transmission power to the other mobile stations.

23. The channel communication method as claimed in claim 17, wherein the second rate change condition is satisfied when a transmission power to the corresponding mobile station is lower than a reference average transmission power to the other mobile stations, a receiving strength of a reverse link is higher than a reference strength value, and a signal-to-noise ratio of the reverse link is higher than a reference signal-to-noise ratio.

24. A channel communication method for a wireless communication system, comprising the steps of:

analyzing an environment of a channel in service to determine whether a rate change condition is satisfied, and sending a rate change request message to a base station when the rate change condition is satisfied; and

upon reception of a response message from a mobile station in response to said rate change request message, switching a presently used coding rate and a presently used orthogonal code, of a channel receiver to a coding rate and an orthogonal code corresponding to information included in the response message from the mobile station;

wherein the step of determining whether a rate change condition is satisfied comprises the steps of;

examining an environment of a channel in communication with the base station;

selecting a coding rate lower than a present coding rate, when a first rate change condition is satisfied; and

selecting a coding rate higher than a present coding rate, when a second rate change condition is satisfied; and

 

wherein the first rate change condition is satisfied when a condition selected from the group consisting of;

condition 1;

an average reverse link transmission power is higher than an upper threshold transmission power;

condition 2;

an average forward link receiving strength is lower than a lower threshold receiving strength; and

condition 3;

an average forward link signal-to-noise ratio is lower than a lower threshold signal-to-noise ratio;

is satisfied.

25. The channel communication method as claimed in claim 24, wherein the second rate change condition is satisfied when a condition selected from the group consisting of:

condition 1;

an average reverse link transmission power is lower than a lower threshold transmission power;

condition 2;

an average forward link receiving strength is higher than an upper threshold receiving strength; and

condition 3;

an average forward link signal-to-noise ratio is higher than an upperthreshold signal-to-noise ratio;

is satisfied.

26. A channel communication method for a wireless communication system, comprising the steps of:

upon reception of a rate change request message from a base station, selecting a coding rate and an orthogonal code according to information included in the request message;

sending a response message to the base station; and

changing a presently used coding rate and orthogonal code of a channel receiver to the selected coding rate and orthogonal code;

wherein said step of selecting a coding rate comprises the steps of;

examining a call condition associated with the mobile station to determine whether the rate change condition is satisfied;

when a first rate change condition is satisfied, selecting a coding rate lower than a present coding rate of the mobile station and selecting an orthogonal code having a length corresponding to the selected coding rate; and

when a second rate change condition is satisfied, selecting a coding rate higher than a present coding rate of the mobile station and selecting an orthogonal code having a length corresponding to the selected coding rate.

27. A channel communication method for a CDMA communication system, comprising the steps of:

(i.) upon reception of a rate change request message from a base station, determining whether a present coding rate and orthogonal code can be changed to a different coding rate and orthogonal code based on information in the request message;

(ii.) when the present coding rate and orthogonal code can be changed, changing the present coding rate and orthogonal code to the different coding rate and orthogonal code, and sending a response message to the base station indicating said changes; and

(iii.) when the present coding rate and orthogonal code cannot be changed, generating and sending a message to the base station indicating that a change cannot occur;

wherein said step of determining whether the present coding rate and orthogonal code can be changed to the different coding rate and orthogonal code based on the information in the request message comprises the steps of;

examining a call condition associated with the mobile station to determine whether the rate change condition is satisfied;

when a first rate change condition is satisfied, selecting a coding rate lower than a present coding rate of the mobile station and selecting an orthogonal code having a length corresponding to the selected coding rate; and

when a second rate change condition is satisfied, selecting a coding rate higher than a present coding rate of the mobile station and selecting an orthogonal code having a length corresponding to the selected coding rate.