WO2001084757A1 - Systemes et procedes de communication utilisant la modulation par intervalle de temps ou la modulation multiporteuse avec amrc-sd - Google Patents

Systemes et procedes de communication utilisant la modulation par intervalle de temps ou la modulation multiporteuse avec amrc-sd Download PDF

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Publication number
WO2001084757A1
WO2001084757A1 PCT/US2000/011819 US0011819W WO0184757A1 WO 2001084757 A1 WO2001084757 A1 WO 2001084757A1 US 0011819 W US0011819 W US 0011819W WO 0184757 A1 WO0184757 A1 WO 0184757A1
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Prior art keywords
information bits
estimated
energy
channel
circuit
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PCT/US2000/011819
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English (en)
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Chunyan Liu
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Chunyan Liu
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Priority to PCT/US2000/011819 priority Critical patent/WO2001084757A1/fr
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/02—Channels characterised by the type of signal
    • H04L5/023—Multiplexing of multicarrier modulation signals
    • H04L5/026—Multiplexing of multicarrier modulation signals using code division

Definitions

  • This invention relates to communication systems and methods using a novel method of time-slot modulation (TSM) or multi-carrier modulation (MCM) combined with a direct-sequence code division multiple access (DS-CDMA) scheme, and accordingly to the manner of operation of communication systems with the invented system built in. More specifically, this invention relates to a multi-user digital communication system where a pre-determined number of information bits for each user are mapped to a pre-determined number N of symbols with one of the N symbols carrying non-zero-energy and all the other N-1 symbols carrying zero-energy. The symbols are then transmitted over N time-slots or multi-carriers after modulating a DS-CDMA spreading code.
  • TSM time-slot modulation
  • MCM multi-carrier modulation
  • DS-CDMA direct-sequence code division multiple access
  • the modulation method used is generally the conventional phase shift keying (PSK) or frequency shift keying (FSK).
  • PSK phase shift keying
  • FSK frequency shift keying
  • the FSK is used.
  • the multiple access methods used are generally the conventional code division multiple access (CDMA), time division multiple access
  • TDMA time division multiple access
  • FDMA frequency division multiple access
  • the IS-95 CDMA scheme combined with the PSK modulation has achieved better efficiency than the TDMA and FDMA schemes by efficiently utilizing the voice-activity property (in more than 50% of time a wireless-phone user is not talking), the soft handoff and the multi-path diversity.
  • the CDMA with the PSK is still not efficient enough to satisfy the demand of more and more wireless users and more bandwidth-demanding services.
  • An object of this invention is to use a novel method of time-slot modulation (TSM) or multi- carrier modulation (MCM) combined with the direct-sequence code-division-multiple-access (DS-CDMA) scheme to improve the bit-error-rate versus signal-to-interference-ratio performance and the capacity performance of a multi-user digital communication system by a large amount, compared to the existing CDMA-PSK method, while the novel method increases the manufacturing complexity and cost by a minimal amount and needs to change the existing DS-CDMA systems slightly.
  • TSM time-slot modulation
  • MCM multi- carrier modulation
  • DS-CDMA direct-sequence code-division-multiple-access
  • Another object of this invention is to design a novel method to demodulate the time-slot- modulated signals or the multi-carrier-modulated signals.
  • Another object of this invention is to design a novel method to demodulate the time-slot- modulated signals or the multi-carrier-modulated signals with the DS-CDMA codes modulated by the signals.
  • Another object of this invention is to design a novel demodulation method for the time-slot modulation or multi-carrier modulation to be functioning effectively in a multi-path fading environment when a mobile user is moving.
  • Another object of this invention is to design a novel channel-estimation method by using a variable-correlation/accumulation length according to an estimated mobile speed.
  • each user is assigned an orthogonal code (such as a Walsh code) and/or a pseudo- noise (PN) sequence.
  • PN pseudo- noise
  • I in- phase
  • Q quadrature
  • PN pseudo- noise
  • FIG. 8.3.2 More implementation details of a frequency-hopping (FH) CDMA system is disclosed in US Patent No. 4222115 by Cooper et al.
  • each user's information bits are used to modulate a radio frequency (RF) carrier whose frequency is determined by a number of PN sequence bits or by one of a set of orthogonal codes, and is hopping in a pseudo-random pattern according to the PN sequence or the orthogonal code.
  • RF radio frequency
  • the FH CDMA method does not provide any effective means to reduce the interference generated by other users, which is a severe problem and limits the capacity of the communication system.
  • the goal of this invention is to use a novel method of time-slot modulation (TSM) or multi- carrier modulation (MCM) combined with the direct-sequence code-division-multiple-access
  • TSM time-slot modulation
  • MCM multi- carrier modulation
  • DS-CDMA bit-error-rate versus signal-to-interference-ratio performance of a multi-user digital communication system without increasing much the complexity of existing DS-CDMA systems.
  • the invented digital communication system comprises a transmitter and/or a receiver for each of the stations (base-stations or user-stations) in the system.
  • the transmitter comprises a time-slot- modulation (TSM) or (multi-carrier-modulation, MCM) integrated circuit (IC) and a DS-CDMA spreading integrated circuit (IC).
  • TSM time-slot- modulation
  • MCM multi-carrier-modulation
  • IC DS-CDMA spreading integrated circuit
  • Both ICs can be implemented by using an application-specific- integrated-circuit (ASIC) or a field-programmable-gate-array (FPGA) or a very high-speed digital signal processor (DSP) and are loaded with the computer-program implementing the TSM or MCM modulation and the DS-CDMA spreading.
  • ASIC application-specific- integrated-circuit
  • FPGA field-programmable-gate-array
  • DSP very high-speed digital signal processor
  • a pre-determined number of information bits for each user are mapped to a pre-determined number N of symbols with one of the N symbols carrying non-zero-energy and all the other N-1 symbols carrying zero-energy.
  • the symbols are then transmitted over N time-slots or multi-carriers after modulating a DS-CDMA spreading code.
  • the receiver of the invented system comprises a DS-CDMA de-spreading IC and a TSM (or MCM) demodulation IC. Both ICs can be implemented by using an ASIC or a FPGA or a DSP and are loaded with the computer-program implementing the TSM or MCM demodulation and the DS-CDMA de-spreading.
  • the TSM (or MCM) demodulation IC comprises a channel estimation circuit, a channel-distortion compensation circuit, a channel-energy estimation circuit and a TSM or MCM inverse mapping circuit which maps the received TSM or MCM symbols back to the transmitted bits.
  • a conventional DS-CDMA system such as the IS-95 CDMA system
  • FIG. 1 is a schematic diagram illustrating one embodiment of a transmitter of a digital communication system employing the time-slot-modulation (TSM) or multi-carrier-modulation (MCM) of the present invention combined with a direct-sequence code-division-multiple-access (DS-CDMA) spreading circuit.
  • TSM time-slot-modulation
  • MCM multi-carrier-modulation
  • DS-CDMA direct-sequence code-division-multiple-access
  • FIG. 2 is a schematic diagram illustrating one embodiment of a receiver of a digital communication system employing the TSM or MCM demodulation of the present invention combined with a DS-CDMA de-spreading circuit.
  • FIG. 3a is a schematic diagram illustrating one implementation of the time-slot-modulation (TSM) of the present invention.
  • FIG. 3b is a schematic diagram illustrating another implementation of the time-slot-modulation (TSM) of the present invention.
  • FIG. 3 c is a schematic diagram illustrating one implementation of the multi-carrier-modulation (MCM) of the present invention.
  • FIG 3d is a schematic diagram illustrating another implementation of the multi-carrier- modulation (MCM) of the present invention.
  • Figure 4a is a schematic diagram illustrating the frame and slot structure of the TSM signal of the present invention.
  • Figure 4b is a schematic diagram illustrating the frame and multi-carrier structure of the MCM signal of the present invention.
  • Figure 5a illustrates a logic flow chart of the software loaded into the TSM-mapping IC chip to implement the function of generating the TSM signal.
  • Figure 5b illustrates a logic flow chart of the software loaded into the MCM-mapping IC chip to implement the function of generating the MCM signal.
  • FIG. 6a is a schematic diagram illustrating one implementation of the TSM demodulation of the present invention.
  • FIG. 6b is a schematic diagram illustrating another implementation of the TSM demodulation of the present invention.
  • Figure 6c is a schematic diagram illustrating one implementation of the MCM demodulation of the present invention.
  • Figure 6d is a schematic diagram illustrating another implementation of the MCM demodulation of the present invention.
  • Figure 7a illustrates a logic flow chart of the software loaded into the TSM-inverse-mapping IC chip to implement the function of demodulating the TSM signal.
  • Figure 7b illustrates a logic flow chart of the software loaded into the MCM-inverse-mapping IC chip to implement the function of demodulating the MCM signal.
  • Figure 8 is schematic diagram illustrating an implementation of the channel-estimation circuit using a method with variable correlation/accumulation according to the vehicle speed.
  • a transmitter of the invented system comprises a time-slot-modulation (TSM) or multi-carrier-modulation (MCM) integrated-circuit (IC) 3, a direct-sequence code- division-multiple-access (DS-CDMA) spreading circuit 40, a speech/video/internet source (possibly with source-encoding) 10, a channel-encoding/interleaving (optional)/data- scrambling/pilot-symbol-multiplexing (optional) circuit 20, an optional circuit 60 generating other channels such as a pilot-channel or other traffic channel, a summing circuit 50 combining all necessary channels together, and a pulse-shaping/RF-modulation circuit 70.
  • TSM time-slot-modulation
  • MCM multi-carrier-modulation
  • DS-CDMA direct-sequence code- division-multiple-access
  • the speech/video/internet source 10 receives the input from a microphone, a computer or a telecommunication network (such as a switch), or any other data sources.
  • the source may be also any other data.
  • the source bits from the source 10 are then channel-encoded, interleaved, scrambled, and optionally multiplexed with pilot symbols at the circuit 20.
  • the channel encoding in the circuit 20 is used to correct and detect errors incurred during the data transmission.
  • the interleaving in the circuit 20 could enhance the channel-coding capability by reducing the burst errors.
  • the source data from the source 10 needs to be scrambled in the circuit 20 in order to make the TSM or MCM more effective in reducing the interference of the invented multi-user digital communication system.
  • pilot symbols may be inserted into the information bits in the circuit 20 and assist in a number of functions in the receiver, such as channel estimation, synchronization acquisition and symbol-timing-recovery.
  • the pilot symbols may be also transmitted through a pilot channel generated in the circuit 60 and combined at the summer 50 with the information traffic channel from the DS-CDMA spreading circuit 40.
  • the preprocessed information bits from the circuit 20 are sent to the TSM or MCM circuit 3 and are converted to TSM or MCM symbols.
  • the TSM or MCM symbols from the TSM or MCM circuit 3 are sent to the DS-CDMA spreading circuit 40, are spread and converted to DS-CDMA spread symbols.
  • the DS-CDMA spread symbols are referred to as DS-CDMA chips.
  • the DS-CDMA chips from the DS-CDMA spreading circuit 40 are sent to the summer circuit 50 and are combined with signals from other channels if necessary.
  • the combined DS-CDMA signal is then sent to the pulse-shaping/RF-modulation circuit 70 for final processing before being sent out to an antenna or cable.
  • a receiver of the invented system comprises a TSM or MCM demodulation integrated circuit (IC) 6, a DS-CDMA de-spreading circuit 120, a RF-demodulation/matched- filtering circuit 110, a channel-decoding/de-interleaving/data-de-scrambling circuit 140 and a speech/video/internet signal processing circuit 150.
  • IC TSM or MCM demodulation integrated circuit
  • DS-CDMA de-spreading circuit 120 a DS-CDMA de-spreading circuit 120
  • a RF-demodulation/matched- filtering circuit 110 a channel-decoding/de-interleaving/data-de-scrambling circuit 140 and a speech/video/internet signal processing circuit 150.
  • the received RF signal which is transmitted by the transmitter shown in Figure 1 is received by an RF antenna or from a cable and is processed by an RF-demodulation/matched-filtering circuit 110 and is converted to a sampled baseband signal.
  • the sampled baseband signal is sent to the
  • DS-CDMA despreading circuit 120 and is despread by using all necessary DS-CDMA codes including PN codes and orthogonal codes, for all necessary channels including traffic channels, pilot channels etc.
  • the despread signal is then sent to the TSM or MCM demodulation IC 6 for further processing and is converted to information bits.
  • the demodulated information bits are then sent to the circuit 140.
  • the bits need to be channel-decoded to correct and detect errors incurred during the transmission.
  • a deinterleaving operation is performed if the bits are interleaved at the transmitter circuit 20.
  • the bits also need to be descrambled to restore the bit order which is scrambled by the transmitter circuit 20.
  • the detected/corrected information bits are sent to the circuit 150 for final processing before being sent to a speaker, a computer or a telecommunication network or any other data terminal.
  • the TSM or MCM IC 3 is illustrated in more detail in Figures 3a, 3b, 3c and 3d.
  • TSM IC An implementation of the TSM IC is illustrated in Figure 3 a, where an information bit stream ...,b(i+R-l), ...,b(i), ...,b(0) is generated by the circuit 20.
  • Each b(i) represents an information bit 0 or 1 at the discrete time interval t j with 7*, to be the period of one information bit, and R represents the number of information bits in a frame.
  • the major TSM modulation circuit is a TSM mapping IC 5a. The operation of the TSM mapping IC 5a is described as follows.
  • Each s(k) represents a TSM symbol at the discrete time interval kT s with T s to be the period of one TSM symbol.
  • Each TSM time-slot has 112 TSM symbols.
  • the first consecutive n information bits b(i+n-l), ...,b(i+l) ,b(i) are mapped to the first TSM symbols of all 2 n'm TSM time-slots of the TSM frame, i.e., 2 n'm TSM symbols s(k+(2 n - m - ⁇ )R/n), ...s(k+R/n),s(k), where the TSM symbol s(k) is the first symbol of the TSM Slot No. 0 in the TSM frame, the TSM symbol s(k+R/n) is the first symbol of the TSM Slot No.
  • the TSM symbol s(k+2R/n) is the first symbol of the TSM Slot No. 2, ..., and the TSM symbol s(k+(2"- m -l)R/n) is the first symbol of the TSM Slot No. 2""*-l .
  • the second consecutive n information bits b(i+2n-l), ...,b(i+n+ ⁇ ) ,b(i+n) are mapped to the second TSM symbols of all T 'm TSM time-slots. And so on.
  • the next 7 consecutive bits b( ⁇ 3), ...,b(8) ,b(7) are mapped to the second TSM symbols of all 32 TSM time-slots, i.e., s(3472+ ⁇ ), ...s ⁇ 12+l),s(l). And so on.
  • the 112th consecutive 7 bits b(l 1 I), ...,b(l 12-6) ,b( ⁇ 12-7) are mapped to the 112th TSM symbols of all 32 TSM time-slots, i.e., s(3472+l 11), ...s(l 12+11 ⁇ ),s( ⁇ 11).
  • the TSM symbol s(k+jR/n) of Slot No./ is chosen to be a 2 m - ⁇ ry phase-shift-keying(PSK)-modulated symbol determined by the remaining m bits of the n bits, e.g., b(i+m-l) ...b(i+l)b(i).
  • TSM symbol s(k+jR/n) of Slot No./ may be also chosen to be a symbol modulated by using any other 2 m -ary modulation scheme, such as the quadrature-amplitude- modulation (QAM).
  • QAM quadrature-amplitude- modulation
  • the TSM is a combination of a 2" " '"-ary orthogonal modulation and a 2 m - ary PSK modulation for m>0. If m ⁇ 0, the TSM becomes a 2"-ary orthogonal modulation.
  • each bit frame has 2R bits b(i+2R-l), ...,b(i+l),b(i) and is de-multiplexed at the circuit 31 into the in-phase (I) frame b ⁇ (i+R-l), and the quadrature (Q) frame b ⁇ ( ⁇ +R-l , ...,b Q (i+ ⁇ ),bQ(i).
  • the I-frame bits b](i+R-l), ...,b ⁇ (i+l),b (i) are mapped at the TSM mapping circuit 32 to 2" "m R/n consecutive TSM I-frame symbols s ⁇ (k+2" 'm R/n- ⁇ ), ..., are independently mapped at the TSM mapping circuit 33 to 2" 'm R/n consecutive TSM Q-frame symbols s Q (k+2"- m R/n-l), ...,s Q (k+(2 n - m - ⁇ )R/n), ...,s Q (k+R/n), ...,s Q (k+l), s Q 0).
  • FIG. 3c An implementation of the MCM IC is illustrated in Figure 3c, where an information bit stream ...,b(i+R- ⁇ ), ...,b(i), ...,b(0) is generated by the circuit 20.
  • Each b(i) represents an information bit 0 or 1 at the discrete time interval iT b with Tj to be the period of one information bit, and R represents the number of information bits in a frame.
  • the major MCM modulation circuit is an MCM mapping IC 5b. The operation of the MCM mapping IC 5b is described as follows.
  • Each S j (k) represents a MCM symbol for the RF carrier No. j at the discrete time interval kT s with T s to be the period of one MCM symbol.
  • ...,b(i+l) ,b(i) are mapped to the first MCM symbols of all 2 n'm MCM time-slots of the MCM frame, i.e., 2 n'm MCM symbols _.- admir. structuri_. (/ ), ...s ⁇ (k),so(k), where the MCM symbol so(k) is the first symbol of the MCM Carrier No. 0 in the MCM frame, the MCM symbol s ⁇ (k) is the first symbol of the MCM Carrier No. 1, the MCM symbol S 2 (k) is the first symbol of the MCM Carrier No. 2, ..., and the MCM symbol »- • .-_ structuri,_. (k) is the first symbol of the MCM Carrier No.
  • n-m bits of the n bits e.g., b(i+n-l) ...b(i+m+l)b(i+m) are used to determine a carrier number Carrier No./ with/- 2 n'm ⁇ b(i+n-l)+ ...
  • the MCM symbol Sj(k) of Carrier No./ is chosen to be a 2 m - ⁇ ry phase-shift-keying(PSK)-modulated symbol determined by the remaining m bits of the n bits, e.g., b(i+m-l)...b(i+l)b(i).
  • Incrementing the index khy 1, incrementing the index i by n and repeating the same operation as the above maps the next consecutive n bits b(i+2n-l), ...,b(i+n+l),b(i+n) to T "m MCM symbols J 2 hinder_ balance,_. (/C + 1), ... ⁇ (k+l),s 0 (k+ 1) with/ 2 n'm'1 b(i+2n-l)+...
  • the MCM symbol s j (k) of Carrier No./ may be also chosen to be a symbol modulated by using any other 2 m - ⁇ ry modulation scheme, such as the quadrature-amplitude- modulation (QAM).
  • QAM quadrature-amplitude- modulation
  • each bit frame has 2R bits b(i+2R-l), ...,b(i+l),b(i) and is de-multiplexed at the MCM mapping circuit 35 into the in-phase (I) frame b ⁇ (i+R-l), ...,b ⁇ (i+l),b ⁇ (i) and the quadrature (Q) frame bQ(i+R-l),
  • Each frame has R information bits, which are mapped to a TSM frame with T 'm R/n TSM symbols.
  • Each TSM frame is divided into m time-slots with Slot No. 0 having R/n TSM symbols s(k+R/n-l), ...,s(k+l),s(k), Slot No. 1 having R/n TSM symbols s(k+2R/n-l), ...,s(k+R/n), and so on, and Slot No. 2 n"m -l having R/n TSM symbols s(k+2"- m R/n-l), ...,s(k+(2"- m -l)R/n).
  • Each TSM symbol may be zero, a PSK- modulated complex number with I and Q components, or a real number if m is chosen to be zero.
  • Each frame has R information bits, which are mapped to a MCM frame with 2 n'm MCM carriers.
  • Carrier No. 0 has R/n MCM symbols s 0 (k+R/n-l), ...,s 0 (k+l) , s 0 (k).
  • Carrier No. 1 has MCM symbols s ⁇ (k+R/n-l), ...,s ⁇ (k+l), s ⁇ (k).
  • Carrier No. 2""*-l has MCM symbols £,,-_,-_.
  • Each MCM symbol may be zero, a PSK- modulated complex number with I and Q components, or a real number if m is chosen to be zero.
  • Figure 5a illustrates a logic flow chart of the software loaded into the TSM mapping IC chip 5a to implement the functions of mapping the information bit stream ...,b(i+R-l), ...,b( ⁇ ), ...,b(0) to the TSM symbols ...s(k+2 n - m R/n-l), ...,s(k+(2"- m -l)R/n), ...,s(k+R/n), ...,s(k+l), s(k).
  • the information bit stream ...,b(i+R-l), ...,b(i), ...,b(0) at step 5a-l is divided into frames with R bits per frame.
  • n information bits b(i+n-l), ...,b(i+l) ,b(i) are picked.
  • (n-m)-hit unsigned binary integer b(i+n-l) ...b(i+m+l)b(i+m) is converted to a decimal number/.
  • the information bits b(i+n-l), ...,b(i+l) ,b(i) are mapped at step
  • the index i is incremented by n and the index k is incremented by 1 at step 5a-8 if all the information bits have not been transmitted. If all the information bits have been transmitted after step 5a-6 or 5a-5, then the process should be terminated. After the indexes i and k have been incremented at step 5a-8, the TSM mapping
  • Figure 5b illustrates a logic flow chart of the software loaded into the MCM mapping IC chip 5b to implement the functions of mapping the information bit stream ...,b(i+R-l), ...,b(i), ...,b(0) to the MCM symbols for 2 n'm carriers, i.e. ... s r ⁇ , _.(/ ) ...for Carrier No. 2 n'm -l, ...s ⁇ (k)... for Carrier
  • step 5b-3 (n-m)-hit unsigned binary integer b(i+n-l) ...b(i+m+l)b(i+m) is converted to a decimal number/.
  • j' 0, l, ..., 2 n'm -l andj' ⁇ j.
  • the index i is incremented by n and the index k is incremented by 1 at step 5b-8 if all the information bits have not been transmitted. If all the information bits have been transmitted after step 5b-6 or 5b- 5, then the process should be terminated. After the indexes / ' and k have been incremented at step 5b-8, the MCM mapping IC goes back to step 5b-2 to start another cycle of the process.
  • the TSM demodulation IC comprises a channel estimation circuit 8, a channel distortion compensation circuit 62, a channel-energy estimation circuit 63 and a TSM inverse-mapping IC 7a.
  • the general method of channel estimation for a DS-CDMA system is known to people with the ordinary art in the field.
  • the known method is to correlate the pilot DS-CDMA chips with received composite DS-CDMA signal and accumulate the correlation result.
  • the known method uses a fixed correlation/accumulation length.
  • the channel estimation circuit 8 can use the known channel-estimation method.
  • Figure 8 Another method of using variable- length correlation/accumulation is illustrated in Figure 8.
  • the channel-estimation result from the circuit 8 is sent to the channel-distortion-compensation circuit 62 and the channel-energy estimation circuit 63.
  • the phase of the received signal is rotated according to the channel-estimation result from the circuit 8.
  • the output signal from the circuit 62 is an estimated TSM symbol stream ...s d (k+2 n'm R/n-l), ...,s d (k+(2 n'm -l)R/n), ...,s d (k+R/n), ...,s d (k+l), s d (k)... s d (0).
  • the channel-estimation result from the circuit 8 is converted to an estimated channel-energy number using a method known to people with an ordinary art in the field.
  • the output of the channel-energy estimation circuit 63 is a stream of positive numbers ...ce(k+2 n - m R/n-l), ..., ce(k+(2"- m -l)R/n), ..., ce(k+R/n), ..., ce(k+l), ce(k)... ce(0).
  • the TSM inverse-mapping IC 7a maps the estimated TSM symbols back to the transmitted information bits.
  • the output from the TSM inverse mapping circuit 7a is an estimated information bit stream ... , b d (i+R- 1), ..., b d (i), ..., b d (0) .
  • FIG. 6b For the TSM signal generated in Figure 3b, an alternative method of implementing the TSM demodulation IC is illustrated in Figure 6b.
  • the method and techniques used for the channel estimation circuit 8, channel-distortion-compensation circuit 66 and the channel-energy estimation circuit 67 are the same as those illustrated in Figure 6a.
  • the output from the circuit 66 is two estimated TSM symbol streams with its in-phase (I) TSM frames ...s ⁇ d (k+2" 'm R/n- 1), ...,sid(k+(2 n'm -l)R/n), ..., s ⁇ d (k+R/n), ..., s ⁇ d (k+l), sj d (k)...
  • the output from the circuit 68 is an estimated information bit stream ...,bid(i+R-l), — d ⁇ ), ...,bu( ).
  • the estimated Q-frame TSM symbols are sent to the TSM inverse mapping circuit 71 and are indenpendly mapped back to the Q-frame information bits transmitted in Figure 3b.
  • the output from the circuit 71 is an estimated information bit stream ...,b Qd (i+R-l), ...,b Qd (i), ...,b Qd (0).
  • the operation of the TSM inverse mapping circuits 68 and 71 is the same as that of the circuit 7a in
  • the MCM demodulation IC comprises a channel estimation circuit 8, a channel distortion compensation circuit 76, a channel-energy estimation circuit 77 and an MCM inverse-mapping IC 7b.
  • the output signal from the circuit 76 is 2 n'm estimated MCM symbol streams, i.e., ...s d o(k+ R/n-l), ..., S d o(k+l) , s d o(k), ..., s d o(0) for Carrier No. 0, MCM symbols ...s d ⁇ (k+R/n-l), ...,s d ⁇ (k+l), s d ⁇ (k), ... , s ⁇ (0) for Carrier No. 1, ..., and MCM symbols ...
  • the output of the channel-energy estimation circuit 77 is 2 n'm streams of positive channel-energy numbers, i.e., ...ceo(k+R/n-l), ..., ceofi+1) , ceo(k), ..., ce 0 (0) for Carrier No. 0, ... ce +R/n- l), ..., ce ⁇ (k+l), ce ⁇ (k), ...
  • the MCM inverse-mapping IC 7b maps the estimated MCM symbols back to the transmitted information bits.
  • the output from the MCM inverse mapping circuit 7b is an estimated information bit stream ... , b (i+R- 1), ..., b d (i), ..., b d (0) .
  • FIG. 6d For the MCM signal generated in Figure 3d, an alternative method of implementing the MCM demodulation IC is illustrated in Figure 6d.
  • the method and techniques used for the channel estimation circuit 8, channel-distortion-compensation circuit 82 and the channel-energy estimation circuit 83 are the same as those illustrated in Figure 6a.
  • the output from the circuit 82 is two groups of estimated MCM symbol streams with its in-phase (I) MCM symbols ...s ⁇ o(k)... for Carrier No. 0, ...s Idl (k) ... for Carrier No. 1, ... s ⁇ ⁇ ⁇ k) ... for Carrier No.
  • the estimated I-frame MCM symbols are sent to the MCM inverse mapping circuit 84 and are mapped back to the I-frame information bits transmitted in Figure 3d.
  • the output from the circuit 84 is an estimated information bit stream ...,b ⁇ d (i+R-l), ...,bu( ⁇ ), ...,bu(0).
  • the estimated Q-frame MCM symbols are sent to the MCM inverse mapping circuit 85 and are independently mapped back to the Q-frame information bits transmitted in Figure 3d.
  • the output from the circuit 85 is an estimated information bit stream ...,bQ d (i+R-l), ...,b Qd (i), ...,bQ d (0).
  • the operation of the MCM inverse mapping circuits 84 and 85 is the same as that of the circuit 7b in Figure 6c.
  • the output bit streams from the circuit 84 and the circuit 85 are multiplexed together to form an estimated information bits stream corresponding to the information bits stream transmitted in Figure 3d.
  • Figure 7a illustrates a logic flow chart of the software loaded into the TSM inverse mapping IC chip 7a to implement the functions of mapping the estimated TSM symbols ...s d (k+2" 'm R/n-l), ..., s d (k+(2" 'm -l)R/n), ...,s d (k+R/n), ...,s d (k+l), s (k)... s d (0) to the information bit stream ...,b (i+R- I), ...,b d (i), ...,b d (0).
  • 2" "w estimated TSM symbols s d (k+(2" 'm -l)R/n), ...,s d (k+R/n), s d (k) are picked.
  • step 7a-2 the total energy of each estimated TSM symbol, i.e., seng(k+(2 n'm -l)R/n), ..., seng(k+R/n), seng(k), is computed which is equal to the sum of the squared-real and squared- imaginary components of each estimated TSM symbol.
  • step 7a-4 the integer/' is incremented by 1.
  • step 7a-5 it is checked whether the product seng(k+jR/n)ce(k+j 'R/n) of the estimated TSM symbol energy at time k+jR/n and the estimated channel energy at time k+j 'R/n is smaller than the product seng(k+j 'R/n)ce(k+jR/n) of the estimated TSM symbol energy at time k+j 'R/n and the estimated channel energy at time k+jRJn.
  • step 7a-9 the decimal number/ is converted to an (n-m)-hit unsigned binary integer b d (i+n-l) ...b (i+m+l)b (i+m).
  • the estimated TSM 2 m -ary-PSK symbol s(k+jR/n) at step 7a- 10 is mapped back to m bits b (i+m-l) ...b d (i+l)b d (i) using a method known to people with the ordinary art in the field.
  • the index i is incremented by n and the index k is incremented by 1 at step 7a- 12 if all the information bits have not been estimated. If all the information bits have been estimated after step 7a-9 and step 7a- 10, then the process should be terminated. After the indexes i and k have been incremented at step 7a-12, the TSM inverse mapping IC 7a goes back to step 7a-a to start another cycle of the process.
  • Figure 7b illustrates a logic flow chart of the software loaded into the MCM inverse mapping IC chip 7b to implement the functions of mapping the estimated MCM symbols ...s d o(k)..., ... s d2 resort.
  • m _ (k) ... to the information bit stream ...,b d (i+R-l), —,bd(i), ...,bd(0).
  • Carrier No. 2" 'm -l are picked.
  • the total energy of each estimated MCM symbol i.e., sengo(k), seng ), ..., seng 2
  • m ⁇ (k) is computed which is equal to the sum of the squared-real and squared-imaginary components of each estimated MCM symbol.
  • the integer/ ' is incremented by 1.
  • n information bits are estimated at step 7b-9 and step 7b- 10
  • the index i is incremented by n
  • the index k is incremented by 1 at step 7b- 12 if all the information bits have not been estimated. If all the information bits have been estimated after step 7b-9 and step 7b- 10, then the process should be terminated.
  • the MCM inverse mapping IC 7b goes back to step 7b-a to start another cycle of the process.
  • variable-correlation/accumulation-length channel estimation IC comprises a mobile-speed estimation circuit 802, a correlation/accumulation- length-adjustment circuit 804 and a conelation/accumulation circuit 806.
  • One method of implementing the mobile-speed estimation circuit 802 is to measure the number of deep-fades vvithin a given period, i.e., the fading rate in the received signal. It is known to people with the ordinary art in the field that a mobile speed in wireless communications is proportional to the fading rate. Therefore The mobile speed can be estimated by mapping the estimated fading rate to the mobile speed according to the proportion coefficients stored in a memory in the IC.
  • the channel estimation accuracy is dependent on the correlation/accumulation- length and the mobile speed.
  • the optimum correlation/accumulation-length is around 3000 chips if the mobile speed is less than 10 km/hour, and around 2300 chips if the mobile speed is 100 km/hour. Therefore a memory mapping table can be stored in the IC 804 and the optimum correlation/accumulation-length can be estimated according to the estimated mobile speed from the circuit 802.
  • the channel can be estimated in the circuit 806 by using a method known to people with the ordinary art in the field, such as by conelating the received signal with the pilot chips and accumulating the correlation result by a length determined in the circuit 804.
  • the carrier used in both the TSM and MCM can be either radio-frequency (RF) electromagnetic-wave, or any other electromagnetic- wave such infrared, laser, or any other light.
  • RF radio-frequency

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)

Abstract

L'invention concerne un système (1) de communication numérique multi-utilisateur, notamment un système de communication sans fil, qui utilise un nouveau procédé de modulation (3) par intervalle de temps (TSM) ou de modulation (3) multiporteuse (MCM) combiné à la logique d'accès multiple par répartition de code (40) à séquence directe (AMRC-SD). Par rapport aux procédés AMRC-MDP existants, le système selon l'invention améliore grandement le rapport entre le taux d'erreur binaire et le rapport signal utile/signal brouilleur ainsi que les performances en termes de capacité du système de communication, même si ce nouveau procédé augmente la complexité de la fabrication et les coûts d'une quantité minime et nécessite une légère modification des systèmes AMCR-SD existants. L'invention concerne également des procédés et des techniques de modulation et de démodulation associés au système selon l'invention.
PCT/US2000/011819 2000-04-29 2000-04-29 Systemes et procedes de communication utilisant la modulation par intervalle de temps ou la modulation multiporteuse avec amrc-sd WO2001084757A1 (fr)

Priority Applications (1)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5504775A (en) * 1993-02-03 1996-04-02 U.S. Philips Corporation Multi-user spread spectrum communication system
US5548582A (en) * 1993-12-22 1996-08-20 U.S. Philips Corporation Multicarrier frequency hopping communications system
US5729570A (en) * 1994-12-08 1998-03-17 Stanford Telecommunications, Inc. Orthogonal code division multiple access communication system having multicarrier modulation

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5504775A (en) * 1993-02-03 1996-04-02 U.S. Philips Corporation Multi-user spread spectrum communication system
US5548582A (en) * 1993-12-22 1996-08-20 U.S. Philips Corporation Multicarrier frequency hopping communications system
US5729570A (en) * 1994-12-08 1998-03-17 Stanford Telecommunications, Inc. Orthogonal code division multiple access communication system having multicarrier modulation

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