Code-division-multiple-access-system based on M-ary pulse-position modulated direct-sequence
First Claim
1. A method of transmitting and receiving a serial data bit stream in a communication system, comprising the steps of:
- (a) converting each group of M consecutive bits of a serial data bit stream which is to be transmitted to a receiver of the communication system into M parallel bits with a bit duration equal to M×
T, where "x" is a multiplication indicator and T is a time duration of a bit in the serial data bit stream, and forming an M-bit vector from the M parallel bits according to a predetermined positive integer M larger than 1, such that serial M-bit vectors converted from serial groups of M consecutive bits form a sequence of M-bit vectors with every M-bit vector having said bit duration equal to M×
T;
(b) selecting a pseudorandom sequence process PNp (t) which has a sequence period Ncp, where Ncp is a positive integer;
(c) dividing each said bit duration equal to M×
T by the sequence period Ncp of the pseudorandom sequence process PNp (t) into Ncp intervals with the time duration of each interval equal to a chip duration Tcp of the pseudorandom sequence process PNp (t), where Tcp =M×
T/Ncp, where "/" is a division indicator;
(d) dividing each of the chip duration Tcp into 2M-1 pulse positions, each pulse position having a time duration Ts, where Ts =Tcp /2M-1 ;
(e) defining a mapping table by which each M-bit vector formed in Step (a) is converted during each said bit duration equal to M×
T into a package of Ncp duty pulses, thus forming a duty pulse package with each duty pulse appearing at a pulse position, which is one of the 2M-1 pulse positions in each Tcp and with a predetermined pulse polarity, the duty pulse packages and the duty pulses in each duty pulse package being generated sequentially to form a duty pulse train;
(f) modulating the duty pulse train formed at Step (e) with a pseudorandom sequence signal PNip (t) to form a pulse-position-modulated-direct-sequence, where PNip (t) is a sample of the pseudorandom process PNp (t) defined at Step (b);
(g) modulating the pulse-position-modulated-direct-sequence formed in Step (f) with a carrier signal to form a carrier modulated signal and transmitting the carrier modulated signal over a channel of the communication system;
(h) receiving as a received carrier modulated signal the carrier modulated signal which is transmitted via the communication channel from the transmitting portion of the communication system;
(i) recovering the Ncp duty pulses in each duty pulse package formed in Step (e) from the received carrier modulated signal by demodulating the received carrier modulated signal synchronously with a local generated carrier signal and pseudorandom sequence signal PNip (t);
(j) determining pulse position and polarity of the Ncp duty pulses in each duty pulse package received, and determining accordingly by using the mapping table defined in Step (e) in a reverse manner the M-bit vector represented by each duty pulse package received; and
(k) converting each M-bit vector determined at step (j) to corresponding M consecutive bits of the serial data bit stream.
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Abstract
A BPSK-MPP-DS-CDMA system is devised using a pulse position modulated direct sequence technique. Under the same bandwidth, same energy used for one decision, and same bit error rate conditions, if the number of users is less than the period Ncp of the pseudorandom sequence signal PNpi (t) used in the BPSK-MPP-DS-CDMA system, the multiple access capacities of the binary (M=2), ternary (M=3), quaternary (M=4), and pentary (M=5) BPSK-MPP-DS-CDMA systems according to the present invention are respectively at least 2, 5.34, 13.28, and 26.4 times greater than that of the conventional BPSK-DS-CDMA systems. On the other hand, if the number of users attains Ncp, the multiple access capacity can not increase any more, however, the bit error rate of the system will be reduced. Furthermore, (M-1)/M transmitting energy is saved.
20 Citations
13 Claims
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1. A method of transmitting and receiving a serial data bit stream in a communication system, comprising the steps of:
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(a) converting each group of M consecutive bits of a serial data bit stream which is to be transmitted to a receiver of the communication system into M parallel bits with a bit duration equal to M×
T, where "x" is a multiplication indicator and T is a time duration of a bit in the serial data bit stream, and forming an M-bit vector from the M parallel bits according to a predetermined positive integer M larger than 1, such that serial M-bit vectors converted from serial groups of M consecutive bits form a sequence of M-bit vectors with every M-bit vector having said bit duration equal to M×
T;(b) selecting a pseudorandom sequence process PNp (t) which has a sequence period Ncp, where Ncp is a positive integer; (c) dividing each said bit duration equal to M×
T by the sequence period Ncp of the pseudorandom sequence process PNp (t) into Ncp intervals with the time duration of each interval equal to a chip duration Tcp of the pseudorandom sequence process PNp (t), where Tcp =M×
T/Ncp, where "/" is a division indicator;(d) dividing each of the chip duration Tcp into 2M-1 pulse positions, each pulse position having a time duration Ts, where Ts =Tcp /2M-1 ; (e) defining a mapping table by which each M-bit vector formed in Step (a) is converted during each said bit duration equal to M×
T into a package of Ncp duty pulses, thus forming a duty pulse package with each duty pulse appearing at a pulse position, which is one of the 2M-1 pulse positions in each Tcp and with a predetermined pulse polarity, the duty pulse packages and the duty pulses in each duty pulse package being generated sequentially to form a duty pulse train;(f) modulating the duty pulse train formed at Step (e) with a pseudorandom sequence signal PNip (t) to form a pulse-position-modulated-direct-sequence, where PNip (t) is a sample of the pseudorandom process PNp (t) defined at Step (b); (g) modulating the pulse-position-modulated-direct-sequence formed in Step (f) with a carrier signal to form a carrier modulated signal and transmitting the carrier modulated signal over a channel of the communication system; (h) receiving as a received carrier modulated signal the carrier modulated signal which is transmitted via the communication channel from the transmitting portion of the communication system; (i) recovering the Ncp duty pulses in each duty pulse package formed in Step (e) from the received carrier modulated signal by demodulating the received carrier modulated signal synchronously with a local generated carrier signal and pseudorandom sequence signal PNip (t); (j) determining pulse position and polarity of the Ncp duty pulses in each duty pulse package received, and determining accordingly by using the mapping table defined in Step (e) in a reverse manner the M-bit vector represented by each duty pulse package received; and (k) converting each M-bit vector determined at step (j) to corresponding M consecutive bits of the serial data bit stream. - View Dependent Claims (4)
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2. A method of transmitting a serial data bit stream from a data source to a communication channel in code-division-multiple-access communication system, comprising the steps of:
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(a) converting each group of M consecutive bits in the serial data bit stream which is to be transmitted to a receiver of the communication system into M parallel bits with a bit duration equal to M×
T, where "x" is a multiplication indicator and T is the time duration of a bit in the serial data bit stream, and forming an M-bit vector from the M parallel bits according to a predetermined positive integer larger than 1, such that serial M-bit vectors converted from serial groups of M consecutive bits form a sequence of M-bit vectors with every M-bit vector having said bit duration equal to M×
T;(b) selecting a pseudorandom sequence process PNp (t) which has a sequence period Ncp, where Ncp is a positive integer; (c) dividing each said bit duration equal to M×
T by the sequence period Ncp of the pseudorandom sequence process PNp (t) into Ncp intervals with the time duration of each interval equal to a chip duration Tcp, of the pseudorandom sequence process PNp (t), where Tcp =M×
T/Ncp, where "/" is a division indicator;(d) dividing each of the chip duration Tcp into 2M-1 pulse positions, each pulse position having a time duration TS, TS =Tcp /2M-1 ; (e) defining a mapping table by which each of the M-bit vectors formed at step (a) is converted during each said bit duration equal to M×
T into a package of Ncp duty pulses, thus forming a duty pulse package with each duty pulse appearing at a pulse position, which is one of the 2M-1 pulse positions in each Tcp, and with a predetermined pulse polarity, the duty pulse packages and the duty pulses in each duty pulse package being generated sequentially to form a duty pulse train;(f) modulating the duty pulse train formed at step (e) with a pseudorandom sequence signal PNip (t) to form a pulse-position-modulated-direct-sequence, where PNip (t) is a sample of the pseudorandom sequence process PNp (t) defined at step (b); (g) modulating the pulse-position-modulated-direct-sequence formed at step (f) with a carrier signal to form a carrier modulated signal, and transmitting the carrier modulated signal to a communication channel of the communication system.
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3. A method of recovering a serial data bit stream from a communication channel in a pulse-position-modulated-direct-sequence code-division-multiple-access communication system, comprising the steps of:
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(a) receiving as a received carrier modulated signal a carrier modulated signal which is transmitted via the communication channel from a transmitting portion of the pulse-position-modulated-direct-sequence code-division-multiple-access communication system; (b) recovering Ncp duty pulses in each duty pulse package from the received carrier modulated signal by demodulating the received carrier modulated signal synchronously with a local generated carrier signal and pseudorandom sequence signal PNip (t), where Ncp is a sequence period of a predetermined pseudorandom sequence process PNp (t) and the pseudorandom sequence signal PNip (t) is a sample of the predetermined pseudorandom sequence process PNp (t), the sequence period Ncp being a positive integer; (c) determining pulse position and pulse polarity of the Ncp duty pulses in each duty pulse package received, and determining accordingly by using a predetermined mapping table in a reverse manner the M-bit vector represented by each received duty pulse package, where M is a positive integer larger than 1; and (d) converting each M-bit vector to corresponding M consecutive bits of the serial data bit stream.
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5. An apparatus for transmitting a serial data bit stream from a data source to a communication channel in a code-division-multiple-access communication system, comprising:
- a serial-to-parallel converter for converting the serial data bit stream into two parallel bit streams and sending out a sequence of 2-bit vectors formed from the two parallel bit streams;
a pulse-position-modulated-direct-sequence modulator for modulating the sequence of 2-bit vectors to a pulse-position-modulated-direct-sequence which has two pulse positions in each chip duration of a pseudorandom sequence signal and has a pulse position of duty pulses in a duty pulse package determined by the 2-bit vector; and a carrier modulator for modulating the pulse-position-modulated-direct-sequence to a modulated signal by a carrier signal and for transmitting the modulated signal to the communication channel. - View Dependent Claims (6, 13)
- a serial-to-parallel converter for converting the serial data bit stream into two parallel bit streams and sending out a sequence of 2-bit vectors formed from the two parallel bit streams;
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7. An apparatus for transmitting a serial data bit stream from a data source to a communication channel in a code-division-multiple-access communication system, comprising:
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a serial-to-parallel converter for converting the serial data bit stream into three parallel bit streams and for sending out a sequence of 3-bit vectors formed from the three parallel bit streams; a pulse-position-modulated-direct-sequence modulator for modulating the sequence of 3-bit vectors to a pulse-position-modulated-direct-sequence which has four pulse positions in each chip duration of a pseudorandom sequence signal and has a pulse position of duty pulses in a duty pulse package determined by the 3-bit vector; and a carrier modulator for modulating the pulse-position-modulated-direct-sequence to a modulated signal by a carrier signal and for transmitting the modulated signal to the communication channel. - View Dependent Claims (8)
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9. An apparatus for transmitting a serial data bit stream from a data source to a communication channel in a code-division-multiple-access communication system, comprising:
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a serial-to-parallel converter for converting the serial data bit stream into M parallel bit streams, where M is a predetermined positive integer larger than 1, and for sending out a sequence of M-bit vectors formed from the M parallel bit streams; a pulse-position-modulated-direct-sequence modulator for modulating the sequence of M-bit vectors to a pulse-position-modulated-direct-sequence which has 2M-1 pulse positions in each chip duration of a pseudorandom sequence signal and has a pulse position of duty pulses in a duty pulse package determined by the M-bit vector; and a carrier modulator for modulating the pulse-position-modulated-direct-sequence to a modulated signal by a carrier signal and for transmitting the modulated signal to the communication channel. - View Dependent Claims (10)
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11. An apparatus of transmitting a serial data bit stream from a data source to a communication channel in a code-division-multiple-access communication system, comprising:
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means for converting the serial data bit stream into M parallel bit streams, so that a sequence of M-bit vectors is formed from the M parallel bit streams, where M is a predetermined positive integer larger than 1; means for modulating the sequence of M-bit vectors to a pulse-position-modulated-direct-sequence which has 2M-1 pulse positions in each chip duration of a pseudorandom sequence signal and has a pulse position of duty pulses in a duty pulse package determined by the M-bit vector; and means for modulating the pulse-position-modulated-direct-sequence to a modulated signal by a carrier signal and for transmitting the modulated signal to the communication channel. - View Dependent Claims (12)
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Specification