Variable rate transmission method, transmitter and receiver using the same

• US 5,896,374 A
• Filed: 10/22/1996
• Issued: 04/20/1999
• Est. Priority Date: 02/23/1995
• Status: Expired due to Term

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Mobile Communications Network Inc. (Nippon Telegraph and Telephone Corporation)
• Inventors: Adachi, Fumiyuki, Okumura, Yukihiko, Ohno, Koji, Higashi, Akihiro
• Primary Examiner(s): HSU, ALPUS
• Application Number:
  US08/732,413
• Time in Patent Office: 910 Days
• Field of Search: 370/470, 370/471, 370/311, 370/216, 370/229, 370/230, 370/232, 370/234, 370/335, 370/342, 370/441, 370/465, 370/509, 370/510, 370/514, 370/545, 370/914, 455/38.2, 455/38.3, 455/68, 455/69, 455/70, 340/825.44, 371/47.1, 371/48, 371/67.1, 375/200, 375/206, 375/365, 375/368
• US Class Current: 370/311
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 2201/70703 using multiple or variable rates
• CPC Class Codes: H04B 2201/70705 Rate detection
• CPC Class Codes: H04B 7/2628 using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] H04B7/2618 takes precedence
• CPC Class Codes: H04J 3/14 Monitoring arrangements for SDH/SONET rings H04J3/085
• CPC Class Codes: H04J 3/1682 Allocation of channels according to the instantaneous demands of the users, e.g. concentrated multiplexers, statistical multiplexers
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/0007 by modifying the frame length
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0013 Rate matching, e.g. puncturing or repetition of code symbols
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0032 Without explicit signalling
• CPC Class Codes: H04L 1/0038 Blind format detection for detection of modulation format H04L27/0012
• CPC Class Codes: H04L 1/0039 other detection of signalling, e.g. detection of TFCI explicit signalling H04L1/0046, H04L27/0012 and H04L25/0262 take precedence
• CPC Class Codes: H04L 1/0046 Code rate detection or code type detection H04L1/0038 takes precedence; detection of the data rate H04L25/0262; for packet format H04L1/0091
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/0063 Single parity check
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0079 Formats for control data H04L1/16 takes precedence; training sequences H04L25/00 and H04L27/00
• CPC Class Codes: H04L 1/0086 : Unequal error protection H04L27/00 and H04L1/004 take precedence for layer 1/2 aspects, e.g. bit loading
• CPC Class Codes: H04L 1/08 : by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 2001/0098 : Unequal error protection
• CPC Class Codes: H04L 7/048 : using the properties of error detecting or error correcting codes, e.g. parity as synchronisation signal
• CPC Class Codes: Y02D 30/50 : in wire-line communication networks, e.g. low power modes or reduced link rate
• CPC Class Codes: Y02D 30/70 : in wireless communication networks

Abstract

A variable rate transmission method that can vary the transmission rate of data. A transmitting side supplies a transmitted data sequence to an error detecting encoder 105 and a frame memory 103. The frame memory 103 stores data of a variable length to be transmitted in one frame. The error detecting encoder 105 calculates an error detecting code (such as CRC code) for each frame of the transmitted data. A multiplexer 104 adds the calculated error detecting code ahead of the transmitted data to place it at the initial position of the frame, and sequentially outputs the data sequence frame by frame. A receiving side calculates an error detecting code of the data in each transmitted frame in the same manner as the transmitting side, and compares the calculated error detecting code with the error detecting code at the initial position of the frame. The end bit of the frame data is decided as a position at which the two error detecting codes coincide. This makes it possible to transmit variable length data without informing the receiving side of the data length in each frame. This is equivalent that the transmission rate can be varied freely.

Claims

1. A variable rate transmission method which varies an average transmission rate by transmitting each frame of a fixed duration, said frame holding data of a variable length,

wherein a transmitting side comprises the steps of:

calculating in each frame an error detecting code of data to be transmitted;

transmitting said data to be transmitted and said error detecting code in said each frame at a predetermined fixed transmission rate; and

pausing transmission in a blank of each frame, said blank being a part of said frame at which said data to be transmitted or said error detecting code is absent,

wherein a receiving side comprises the steps of;

receiving said each frame at said fixed transmission rate;

detecting said error detecting code in said each frame; and

recovering said transmitted data of the variable length in said each frame in response to a detecting result of said error detecting code,

wherein said step of detecting said error detecting code sequentially divides received data in said each frame by predetermined data while shifting said received data bit by bit, and decides that said error detecting code is detected at a point at which said received data can be divided.

2. The variable rate transmission method as claimed in claim 1, wherein said step of recovering said transmitted data decides an end bit position of said transmitted data at a point preceding the point at which said error detecting code is detected by the number of bits of said error detecting code.

3. A variable rate transmission method which varies an average transmission rate by transmitting each frame of a fixed duration, said frame holding data of a variable length,

wherein a transmitting side comprises the steps of:

calculating in each frame an error detecting code of data to be transmitted;

periodically inserting pilot symbols of a known pattern into said each frame;

disposing important data of said data to be transmitted near said pilot symbols;

transmitting said data to be transmitted and said error detecting code in said each frame at a predetermined fixed transmission rate; and

pausing transmission in a blank of each frame, said blank being a part of said frame at which said data to be transmitted or said error detecting code is absent, and

wherein a receiving side comprises the steps of;

receiving said each frame at said fixed transmission rate;

detecting said pilot symbols;

compensating said transmitted data and said error detecting code which are received using said pilot symbols which are detected;

relocating said transmitted data to its original order;

detecting said error detecting code in said each frame; and

recovering said transmitted data of the variable length in said each frame in response to a detecting result of said error detecting code.

4. The variable rate transmission method as claimed in claim 3, wherein said step of disposing said important data near said pilot symbols comprises the steps of:

placing said important data at an initial position of said data to be transmitted;

writing said data to be transmitted row by row into a memory with N rows and M columns alternately from a top row and a bottom row of said memory, where N and M are positive integers;

reading from said memory, column by column, said data to be transmitted which has been stored in said memory; and

inserting said pilot symbols each time said column is read.

5. The variable rate transmission method as claimed in claim 3, wherein said method is CDMA (Code Division Multiple Access), in which said transmitting side further comprises the steps of performing primary modulation of said data to be transmitted and said error detecting code, and performing secondary modulation of a signal which has undergone said primary modulation using a spreading code sequence.

6. The variable rate transmission method as claimed in claim 5, wherein transmission power is increased when transmitting said pilot symbols and said important data.

7. A variable rate transmission method which varies an average transmission rate by transmitting each frame of a fixed duration, said frame holding data of a variable length,

wherein a transmitting side comprises the steps of:

calculating in each frame an error detecting code of data to be transmitted;

transmitting said data to be transmitted and said error detecting code in said each frame at a predetermined fixed transmission rate;

pausing transmission in a blank of each frame, said blank being a part of said frame at which said data to be transmitted or said error detecting code is absent;

when a total amount of said data to be transmitted and said error detecting code is equal to or less than 1/K of a maximum amount of data that can be transmitted by one frame, generating repeat frames, in each of which each bit of said data to be transmitted and said error detecting code is repeated K times;

transmitting said repeat frames at a transmission power of 1/K of transmission power used when said each bit is not repeated; and

informing said receiving side that said data to be transmitted and said error detecting code are repeated K times in said repeat frames, where K is a positive integer,

wherein a receiving side comprises the steps of;

receiving said each frame at said fixed transmission rate;

detecting said error detecting code in said each frame;

recovering said transmitted data of the variable length in said each frame in response to a detecting result of said error detecting code; and

recovering original data from said repeat frames by thinning out data using said K informed from said transmitting side.

8. The variable rate transmission method as claimed in claim 7,

wherein said transmitting side further comprises the steps of:

periodically inserting pilot symbols of a known pattern into said each frame; and

disposing important data of said data to be transmitted near said pilot symbols in said each frame, and

wherein said receiving side further comprises the steps of;

detecting said pilot symbols;

compensating said transmitted data and said error detecting code which have been received using said pilot symbols detected; and

relocating said transmitted data received to its original order.

9. A variable rate transmission method which varies an average transmission rate by transmitting frames of a fixed duration, each frame holding data of a variable length,

wherein a transmitting side comprises the steps of:

calculating in each frame an error detecting code of data to be transmitted;

allocating said frames to a plurality of channels;

periodically inserting pilot symbols of a known pattern into each frame of one of said plurality of channels;

disposing important data of said data to be transmitted near said pilot symbols;

transmitting said data to be transmitted and said error detecting code in said each frame of said plurality of channels at a predetermined fixed transmission rate;

pausing transmission in a blank of each frame, said blank being a part of said frame at which said data to be transmitted or said error detecting code is absent;

spreading said data to be transmitted simultaneously using different spreading code sequences assigned to said plurality of channels to transmit spread data through each channel, and

wherein a receiving side comprises the steps of;

simultaneously receiving said plurality of channels at said fixed transmission rate;

detecting pilot symbols of said one of said plurality of channels;

compensating received signals of said plurality of channels using pilot symbols detected;

relocating said transmitted data received to its original order;

detecting said error detecting code in said each frame; and

recovering said transmitted data of the variable length in said each frame in response to a detecting result of said error detecting code.

10. The variable rate transmission method as claimed in claim 9, wherein data of said plurality of channels are transmitted with a phase of a carrier of each of said plurality of channels being shifted.

11. The variable rate transmission method as claimed in any one of claims 3-6 and 8-10, wherein said important data is control data.

12. A variable rate transmission method which varies an average transmission rate by transmitting each frame of a fixed duration, said frame holding data of a variable length,

wherein a transmitting side comprises the steps of:

calculating in each frame an error detecting code of data to be transmitted;

disposing said error detecting code at a fixed position in and relative to said each frame;

transmitting said data to be transmitted and said error detecting code in said each frame at a predetermined fixed transmission rate; and

pausing transmission in a blank of each frame, said blank being a part of said frame at which said data to be transmitted or said error detecting code is absent, and

wherein a receiving side comprises the steps of;

receiving said each frame at said fixed transmission rate;

extracting said error detecting code placed at said fixed position in said each frame;

detecting an error detecting code in said each frame;

obtaining the number of bits of said transmitted data on the basis of said error detecting code; and

recovering said transmitted data of the variable length in said each frame in response to the obtained number of bits of said transmitted data.

13. The variable rate transmission method as claimed in claim 12, wherein:

said method is a CDMA data transmission method in which said transmitting side further comprises the steps of performing primary modulation of said data to be transmitted and said error detecting code in said each frame, and performing secondary modulation of primary modulated data in each frame by using a spreading code sequence.

14. The variable rate transmission method as claimed in claim 13, wherein:

said transmitting side further comprises the step of performing error correcting encoding and interleaving of said data to be transmitted before said primary modulation, and

said receiving side further comprises the steps of performing a primary demodulation of said transmitted data which is received, and performing deinterleaving and error correcting decoding of said transmitted data which have undergone said primary demodulation.

15. The variable rate transmission method as claimed in claim 12,

wherein said transmitting side further comprises the steps of:

repeating each bit of said data to be transmitted and said error detecting code K times, where K is a positive integer, when a total amount of said data to be transmitted and said error detecting code in said each frame is equal to or less than 1/K of a maximum amount of data that can be transmitted by said each frame;

reducing transmission power of each frame having bits repeated K times to 1/K of a transmission power used when a bit is not repeated; and

wherein said receiving side further comprises the steps of;

integrating over K bit interval said transmitted data and said error detecting code which have been received which includes bits repeated K times; and

recovering said transmitted data by performing thinning out processing of integrated data for every K bits.

16. A variable rate transmission method which varies an average transmission rate by transmitting each frame of a fixed duration, said frame holding data of a variable length,

wherein a transmitting side comprises the steps of:

calculating in each frame an error detecting code of data to be transmitted;

adding to a fixed position in said each frame, transmission rate information representative of the number of bits of data in said each frame and said error detecting code;

transmitting said data to be transmitted, said transmission rate information and said error detecting code in said each frame at a predetermined fixed transmission rate; and

pausing transmission in a blank of each frame, said blank being a part of said frame at which said data to be transmitted or said error detecting code is absent, and

wherein a receiving side comprises the steps of;

receiving said each frame at said fixed transmission rate;

obtaining an end bit position of said transmitted data in each said frame in response to said transmission rate information;

calculating error detecting code of said transmitted data to said end position;

comparing said calculated error detecting code with said error detecting code which has been received;

deciding that said transmitted data to said end bit position is correct when a compared result of the step of comparing coincides; and

recovering said transmitted data of the variable length in said each frame.

17. The variable rate transmission method as claimed in claim 16, wherein:

said transmission method is a CDMA data transmission method in which said transmitting side further comprises the steps of performing primary modulation of said data to be transmitted, said transmission rate information and said error detecting code in said each frame, and performing secondary modulation of primary modulated data in each frame by using a spreading code sequence.

18. The variable rate transmission method as claimed in claim 17,

wherein said transmitting side further comprises the steps of:

performing error correcting encoding of said data to be transmitted, said transmission rate information and said error detecting code in said each frame before said primary modulation;

interleaving error correcting encoded data in said each frame; and

performing said primary modulation of interleaved data, and

wherein said receiving side further comprises the steps of;

despreading data in said each frame which is received by using a spreading code sequence;

performing a primary demodulation of a despread signal; and

deinterleaving transmission data which has undergone said primary demodulation.

19. The variable rate transmission method as claimed in claim 16,

wherein said transmitting side further comprises the step of:

placing said transmission rate information associated with a current frame at a fixed position in a preceding frame, and

wherein said receiving side further comprises the steps of;

extracting said transmission rate information received in said preceding frame; and

deciding an end bit position of data in said current frame in response to said transmission rate information which has been extracted.

20. The variable rate transmission method as claimed in claim 19,

wherein said transmitting side further comprises the steps of:

performing error correcting encoding of data in said each frame;

interleaving said each frame;

performing primary modulation of said each frame which has been interleaved; and

performing secondary modulation of primary modulated transmission data in said each frame by using a spreading code sequence, and

wherein said receiving side further comprises the steps of;

performing a primary demodulation of said transmission data which has been received;

deinterleaving said transmission data which has undergone said primary demodulation.

21. The variable rate transmission method as claimed in any one of claims 16-20,

wherein said transmission side further comprises:

when the number of bits of said transmitted data in said each frame is equal to or less than 1/K of the maximum number of bits of data that can be transmitted by said each frame, where K is a positive integer, repeating each bit of said data to be transmitted K times; and

reducing transmission power of said each frame which has bits repeated K times to 1/K of a transmission power used when a bit is not repeated, and

wherein said receiving side further comprises;

integrating over a K bit interval said transmitted data which has been received which includes bits repeated K times; and

recovering said transmitted data by performing thinning out processing of integrated data for every K bits.

22. A transmitter which varies an average transmission rate by transmitting each frame of a fixed duration, said frame holding data of a variable length, said transmitter comprising:

a memory for storing said data to be transmitted;

pilot symbol inserting means for periodically inserting pilot symbols of a known pattern into said each frame;

data relocating means for disposing near said pilot symbols important data of said data to be transmitted stored in said memory;

means for calculating in said each frame an error detecting code of data to be transmitted; and

means for transmitting said data to be transmitted and said error detecting code in said each frame at a predetermined fixed transmission rate, and for pausing transmission in a blank of each frame, said blank being a part of said frame at which said data to be transmitted or said error detecting code is absent.

23. The transmitter as claimed in claim 22, wherein:

said data relocating means disposes said important data near said pilot symbols by writing said data to be transmitted into said memory row by row with a length of M bits and by reading said stored data to be transmitted from said memory column by column with a length of N bits, wherein N is the number of bits of a slot sandwiched by said pilot symbols, and M is the number of said slots contained in said each frame.

24. The transmitter as claimed in claim 23, wherein:

said data relocating means writes said important data into said memory alternately from a top row and a bottom row of said memory.

25. The transmitter as claimed in any one of claims 22-24, further comprising:

a primary modulator for modulating data in said each frame including said data to be transmitted;

a secondary modulator for performing secondary modulation that spreads data of said each frame which has undergone said primary modulation using a spreading code sequence; and

wherein said pilot symbol inserting means is connected between said primary modulator and said secondary modulator, and periodically inserts said pilot symbols between slots.

26. The transmitter as claimed in claim 24, further comprising:

a transmission power control means connected to said pilot symbol inserting means for controlling transmission power of data in said each frame in accordance with a degree of importance of said data.

27. The transmitter as claimed in claim 26, wherein:

a predetermined particular code is written in a blank in said each frame, said blank occurring when the number of bits of said transmitted data is less than the maximum number of bits of said each frame, and

said transmission power control means reduces transmission power of said blank to zero in accordance with said code.

28. The transmitter as claimed in claim 27, further comprising:

a repeater preceding said memory for repeating said transmitted data and said error detecting code K times for each bit,

wherein said transmission power control means reduces transmission power of said each frame having bits repeated K times to 1/K as compared with transmission power used when said repeating K times is not performed.

29. A transmitter which varies an average transmission rate by transmitting each frame of a fixed duration, said frame holding data of a variable length, said transmitter comprising:

means for calculating in said each frame an error detecting code of data to be transmitted;

pilot symbol inserting means for periodically inserting pilot symbols of a known pattern into said each frame;

a memory for storing said data to be transmitted, said memory capable of reading multiple sets of transmitted data to be transmitted in association with a plurality of channels;

means for pausing transmission in a blank of each frame, said blank being a part of said frame at which said transmitted data or said error detecting code is absent;

data relocating means for writing data into said memory such that important data of said transmitted data to be transmitted stored in said memory is placed near said pilot symbols;

a plurality of primary modulators for primary modulating said multiple sets of transmitted data at a predetermined fixed transmission rate;

a plurality of transmission power control means for controlling transmission power of said each frame output from said primary modulators;

a plurality of secondary modulators for spreading data in said each frame output from said transmission power control means by using different spreading code sequences; and

an adder for adding multiple signals output from said secondary modulators, wherein said data relocating means divides said data to be written into said memory, simultaneously reads from said memory said multiple sets of data which have been formed by the dividing, and supplies read data to said plurality of primary modulators, said pilot symbol inserting means is connected after one of said plurality of primary modulators for periodically inserting said pilot symbols, and said plurality of transmission power control means increase transmission power while transmitting said important data.

30. The transmitter as claimed in claim 29, further comprising:

a plurality of phase controllers each connected after said plurality of primary modulators for shifting phases of carriers of said secondary modulators.

31. A transmitter which varies an average transmission rate by transmitting each frame of a fixed duration, said frame holding data of a variable length, said transmitter comprising:

means for calculating in said each frame an error detecting code of data to be transmitted;

means for adding said error detecting code to a fixed position in and relative to said each frame; and

means for transmitting said data to be transmitted and said error detecting code in said each frame at a predetermined fixed transmission rate, and for pausing transmission in a blank of each frame, said blank being a part of said frame at which said data to be transmitted or said error detecting code is absent.

32. The transmitter as claimed in claim 31, further comprising:

means for performing error correcting encoding of data in said each frame;

means for interleaving data which has undergone said error correcting encoding;

means for primary modulating interleaved data; and

means for secondary modulating primary modulated data by using a spreading code.

33. The transmitter as claimed in claim 31 or 32, further comprising:

means for repeating K times each bit of data in said each frame when the number of bits of said data in said each frame is equal to or less than 1/K of the maximum number of bits that can be transmitted in one frame, where K is a positive integer; and

transmission power control means for reducing transmission power of said each frame having bits repeated K times to 1/K in comparison with transmission power used when said repeating K times is not performed.

34. A transmitter which varies an average transmission rate by transmitting each frame of a fixed duration, said frame holding data of a variable length, said transmitter comprising:

means for calculating in said each frame an error detecting code of data to be transmitted;

adding means for adding, to a fixed position in and relative to said each frame, transmission rate information representative of the total number of data in said each frame and said error detecting code; and

means for transmitting said data to be transmitted, transmission rate information and said error detecting code in said each frame at a predetermined fixed transmission rate, and for pausing transmission in a blank of each frame, said blank being a part of said frame at which said data to be transmitted or said error detecting code is absent.

35. The transmitter as claimed in claim 34, further comprising:

means for performing error correcting encoding of said data to be transmitted, said transmission rate information, and said error detecting code in said each frame;

means for interleaving data which has undergone said error correcting encoding;

means for primary modulating interleaved data; and

means for secondary modulating primary modulated data by using a spreading code.

36. The transmitter as claimed in claim 34, further comprising:

means for adding said transmission rate information associated with a current frame to a fixed position in a preceding frame.

37. The transmitter as claimed in claim 36, further comprising:

means for performing error correcting encoding of said data to be transmitted, said transmission rate information, and said error detecting code in said each frame;

means for interleaving data which has undergone said error correcting encoding;

means for primary modulating interleaved data; and

means for secondary modulating primary modulated data by using a spreading code.

38. The transmitter as claimed in any one of claims 34-37, further comprising:

means for repeating K times each bit of data in said each frame when the number of bits of said data in said each frame is equal to or less than 1/K of the maximum number of bits that can be transmitted in one frame, where K is a positive integer; and

transmission power control means for reducing transmission power of said each frame having bits repeated K times to 1/K in comparison with transmission power used when said repeating K times is not performed.

39. A receiver, comprising:

means for receiving, at a fixed transmission rate, frames which each include transmitted data;

detecting means for detecting error detecting code in said each frame; and

means for recovering said transmitted data of a variable length in said each frame in response to a detection result of said error detecting code,

wherein said detecting means sequentially divides received data in each said frame by predetermined data while shifting said received data bit by bit, and decides that said error detecting code is detected at a point at which said received data can be divided.

40. A receiver, comprising:

means for receiving, at a fixed transmission rate, frames which each include transmitted data;

means for detecting error detecting code in said each frame;

means for recovering said transmitted data of a variable length in said each frame in response to a detection result of said error detecting code;

means for detecting pilot symbols of a known pattern, which are inserted into said each frame periodically;

a memory for storing data transmitted in said each frame; and

data relocating means for rearranging data written in said memory to an original order when receiving transmitted data in said each frame which has important data disposed near said pilot symbols.

41. The receiver as claimed in claim 40, wherein:

said data relocating means rearranges said data in said each frame into the original order by writing said data in said each frame into said memory column by column with a length of N bits, and by reading said stored data of said each frame from said memory row by row with a length of M bits, wherein N is the number of bits of a slot sandwiched by said pilot symbols, and M is the number of said slots contained in said each frame.

42. The receiver as claimed in claim 41, wherein:

said data relocating means carries out reading of said memory alternately from a top row and a bottom row of said memory.

43. The receiver as claimed in any one of claims 40-42, further comprising:

a secondary demodulator for despreading received data by using a spreading code sequence;

a compensator for compensating said data in said each frame by using said pilot symbols; and

a primary demodulator for demodulating said data which has been compensated by said compensator.

44. The receiver as claimed in claim 43, further comprising:

means for integrating over K bit interval said data in said each frame which has been received and which has bits repeated K times; and

means for recovering said transmitted data by performing thinning out of the integrated data at every K bits.

45. A receiver comprising:

a plurality of secondary demodulators for despreading each of a multiple series of frames simultaneously transmitted through a plurality of channels;

a compensator for compensating data in said multiple series of frames by using pilot symbols which are periodically inserted into one of said multiple series of frames and which are sent through one of said plurality of channels;

a plurality of primary demodulators for demodulating compensated data;

a memory for storing said multiple series of data at the same time;

data relocating means for rearranging important data disposed near said pilot symbols to its original order by simultaneously writing said multiple series of frames in separated areas of said memory, and by reading written data in an order different from that of writing;

means for detecting error detecting code in said each frame; and

means for recovering said transmitted data of a variable length in said each frame in response to a detection result of said error detecting code.

46. The receiver as claimed in claim 45, further comprising:

phase controllers each provided for each one of said channels for correcting phases of said multiple series of data.

47. A receiver comprising:

a secondary demodulator for despreading a received spread signal, and for outputting a despread signal;

a primary demodulator for recovering data in each frame from said despread signal;

an error detecting code memory for storing said error detecting code placed at a fixed position in said each frame;

means for calculating an error detecting code from said data in said each frame; and

comparing means for comparing said calculated error detecting code with said error detecting code stored in said error detecting code memory,

wherein the number of bits of variable bit data in said each frame is obtained in response to a result of the comparison.

48. The receiver as claimed in claim 47, further comprising:

means for deinterleaving data output from said primary demodulator; and

means for performing error correcting decoding of the data which has been deinterleaved.

49. The receiver as claimed in claim 47 or claim 48, further comprising:

means for integrating over a K bit interval said data in said each frame which has been received; and

means for recovering said transmitted data by performing thinning out of the integrated data at every K bits.

50. A receiver, comprising:

means for receiving, at a fixed transmission rate, frames which include transmitted data, transmission rate information and an error correcting code;

means for obtaining an end bit position of said transmitted data in each said frame which has been received in response to said transmission rate information which is placed at a fixed position of said each frame, said end bit position determining the number of bits of said transmitted data in said each frame;

means for calculating error detecting code of said transmitted data to said end position;

means for comparing the calculated error detecting code with said error detecting code which has been transmitted in said each frame; and

means for deciding that said transmitted data to said end bit position is correct in said each frame when a compared result coincides.

51. The receiver as claimed in claim 50, further comprising:

a secondary demodulator for despreading a received spread signal and for outputting a despread signal;

a primary demodulator for recovering data in each frame from said despread signal;

means for deinterleaving data output from said primary demodulator;

first means for performing error correcting decoding of said transmission rate information and said error detecting code among data output from said means for deinterleaving; and

second means for performing error correcting decoding of said transmitted data to its end bit position in response to a result of said first means.

52. The receiver as claimed in claim 50, wherein:

said means for deciding determines the end bit position of said transmitted data in a current frame in accordance with said transmission rate information received in a preceding frame.

53. The receiver as claimed in claim 52, further comprising:

a secondary demodulator for despreading a received spread signal and for outputting a despread signal;

a primary demodulator for recovering data in each frame from said despread signal;

means for deinterleaving data output from said primary demodulator;

means for performing error correcting decoding of said transmission rate information and said error detecting code among data output from said means for deinterleaving; and

means for performing error correcting decoding of said transmitted data to its end bit position in response to a result of said error correcting decoding of said transmission rate information received in a preceding frame.

54. The receiver as claimed in any one of claims 50-53, further comprising:

means for integrating over a K bit interval said data in said each frame which has been received when the number of bits of data in said each frame is equal to or less than 1/K of a maximum number of bits that can be transmitted by one frame, where K is a positive integer; and

means for recovering said transmitted data by performing thinning out of the integrated data at every K bits.

55. A variable rate transmission method, comprising the steps of:

inserting pilot symbols of a known pattern into each frame periodically and disposing important data of data to be transmitted near said pilot symbols;

detecting said pilot symbols;

compensating by the detected pilot symbols said data to be transmitted and error detecting code which have been received; and

rearranging said data to be transmitted which has been received to its original order,

wherein said step of disposing said important data near said pilot symbols comprises the steps of;

placing said important data at an initial position of said data to be transmitted;

writing said data to be transmitted row by row into a memory with N rows and M columns alternately from a top row and a bottom row of said memory;

reading from said memory, column by column, said data which has been stored in said memory; and

inserting said pilot symbols each time said column is read.

56. The variable rate transmission method as claimed in claim 55, wherein:

said method is a CDMA data transmission method further comprising the steps of performing primary modulation of said data to be transmitted and said error detecting code in said each frame, and performing secondary modulation of primary modulated data in each frame by using a spreading code sequence.

57. The variable rate transmission method as claimed in claim 56, wherein transmission power is increased when transmitting said pilot symbols and said important data.