Europäisches Patentamt *EP001406421A2* (19) European Patent Office

Office européen des brevets (11) EP 1 406 421 A2

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication: (51) Int Cl.7: H04L 27/34 07.04.2004 Bulletin 2004/15

(21) Application number: 03256098.9

(22) Date of filing: 29.09.2003

(84) Designated Contracting States: • Hayashi, Takahiro, c/o NTT DoCoMo Inc. AT BE BG CH CY CZ DE DK EE ES FI FR GB GR Tokyo 100-6150 (JP) HU IE IT LI LU MC NL PT RO SE SI SK TR • Futakata, Toshiyuki, c/o NTT DoCoMo Inc. Designated Extension States: Tokyo 100-6150 (JP) AL LT LV MK (74) Representative: (30) Priority: 03.10.2002 JP 2002291571 Luckhurst, Anthony Henry William MARKS & CLERK, (71) Applicant: NTT DoCoMo, Inc. 57-60 Lincoln’s Inn Fields Tokyo 100-6150 (JP) London WC2A 3LS (GB)

(72) Inventors: • Moon, Sung Uk, NTT DoCoMo Inc. Tokyo 100-6150 (JP)

(54) Data transmission using hierarchical

(57) A modulation device comprises a modulation ta having been subjected to us- unit (2) that modulates data in a hierarchical manner us- ing multiple types of modulation techniques, and a de- ing multiple types of modulation techniques, and a trans- modulation unit (6) that demodulates the hierarchical mission unit (3) that transmits the hierarchically modu- modulation data using a technique corre- lated data. A demodulation device comprises a receiv- sponding to a specific hierarchy of the hierarchical mod- ing unit (4) that receives the hierarchical modulation da- ulation data. EP 1 406 421 A2

Printed by Jouve, 75001 PARIS (FR) 1 EP 1 406 421 A2 2

Description with the above-described QPSK under the same trans- mission rate, the occupied band-width of 16-QAM is nar- BACKGROUND OF THE INVENTION rower than that of QPSK. This means that 16-QAM is more effective to realize high-speed digital data trans- [0001] The present invention generally relates to 5 mission. However, 16-QAM is easily influenced by fad- modulation and demodulation in digital data transmis- ing, which is the phenomenon of sharp fluctuation in in- sion, and more particularly to a modulation and demod- tensity level of a radio wave due to environmental ulation technique capable of dealing with multiple types change including time and the distance between the of modulation based on hierarchical modulation. transmitter and the receiver. The 16-QAM is mainly used [0002] In recent radio communications, digital modu- 10 for digital MCA ( business). lation techniques are employed in, for instance, cellular [0007] Since the above-described two modulation phone networks, BS television broadcast, and other dig- techniques, QPSK and 16-QAM, are used in digital mo- ital communication networks. Known modulation tech- bile telecommunications, hardware capable of dealing niques used in digital mobile communications include with these two modulation techniques is desirable. Such quadrature phase shift keying (QPSK) and quadrature 15 hardware is advantageous for both users and manufac- (QAM). turers, reducing the cost of components and the space [0003] Quadrature phase shift keying (QPSK) is a for accommodating the hardware, while improving op- modulation technique that uses two carriers out of erability. From this standpoint, JPA 9-27426 proposes a phase by 90 degrees (that is, quarternary signal states), demodulation technique for demodulating both QAM allowing 2 bits/symbol transmission. FIG. 1 is a QPSK 20 modulation signals and QPSK modulation signals in one signal constellation, in which the in-phase component system. and the guadrature component of the QPSK modulation [0008] However, in spite of the existence of multiple signal are expressed in the phase plane defined by the modulation techniques used in digital telecommunica- I-axis (representing the real number) and the Q-axis tions, the transmission ability and the receiving ability (representing the imaginary number). The signal con- 25 are not always consistent with each other. If a receiver stellation is also called "signal diagram". In QPSK mod- is capable of dealing with only QPSK modulation sig- ulation, modulation signals with four different phases nals, 16-QAM modulation signals transmitted from a are arranged at the vertexes of a square. In other words, transmitter cannot be demodulated. To overcome this the transmission signal is represented by one of the four problem, a 16-QAM demodulator has to be furnished in phases. 30 the receiver, in addition to the QPSK demodulator, or [0004] Another type of QPSK modulation is pi/4-shift alternatively, a system proposed in JPA 9-275426 is re- QPSK, which is derived from the above-described quired. The former method causes the circuit scale and QPSK and used in personal digital cellular (PDC) the cost to increase because an extra demodulator has phones based on the second generation mobile com- to be added to the receiver. The latter method provides munications standard. With pi/4-shift QPSK, the phase 35 two independent signal paths, one functioning as a QAM of the carrier rotates by pi/4 per symbol, providing quar- demodulator when receiving a QAM modulation signal, states. and the other functioning as a QPSK demodulator when [0005] In W-CDMA in FDD mode, which is one of the receiving a QPSK modulation signal. One of these two radio transmission protocols used in the third generation demodulation types is selected depending on the mod- cellular systems based on the International Mobile Tel- 40 ulation type of the received signal. Accordingly, it is es- ecommunications-2000 (IMT-2000) standard, BPSK sential to furnish the functions of a QAM demodulator (binary phase shift keying) is used for uplink data mod- and a QPSK demodulator in the circuit structure. ulation, while QPSK is used for downlink data modula- tion. In TDD mode, QPSK is employed for data modu- SUMMARY OF THE INVENTION lation on both uplink and downlink. 45 [0006] Another known modulation technique is [0009] The present invention is conceived to over- 16-QAM (quadrature amplitude modulation), which al- come the above-described problems, and it is an object lows 4 bits/symbol data transmission using a combina- of the invention to provide a modulation/demodulation tion of phase and amplitude of the carrier representing technique that allows received data to be demodulated one of sixteen (16) four-bit patterns. FIG. 2 is an exam- 50 according to the demodulation ability of the receiver ple of a 16-QAM signal constellation. With 16-QAM, four even if the demodulation ability on the receiving side is bits (16 patterns) of an input sequence are divided into not totally consistent with the modulation functions of four 2-bit patterns. The two carriers out of phase by 90 the transmission side apparatus. degrees are amplitude-modulated in the respective four [0010] To achieve the object, in one aspect of the in- signal states, and synthesized. The constellation plotted 55 vention, a modulation device is furnished with a hierar- after the amplitude modulation is shown in FIG. 2. The chical modulation function. To be more precise, the divisions on the I-axis and the Q-axis are -0.9487, modulation device comprises a modulation unit that -0.3162, 0.3162, and 0.9487. Comparing the 16-QAM modulates data in a hierarchical manner using multiple

2 3 EP 1 406 421 A2 4 types of modulation techniques, and a transmission unit modulation functions, the optimum demodulation type that transmits the hierarchically modulated data. is selected, taking into account the propagation environ- [0011] The modulation device further comprises a ment and other factors. Consequently, telecommunica- sampling pattern generating unit that generates a sam- tions can be maintained without undesirable disconnec- pling pattern for each of the modulation techniques. The 5 tion even if the propagation environment abruptly sampling pattern defines a sampling space for quantiz- changes. ing said data in accordance with each of said modulation techniques. In this case, the modulation unit modulates BRIEF DESCRIPTION OF THE DRAWINGS said data in the hierarchical manner using a sampled based on the sampling pattern. 10 [0019] [0012] The sampling pattern defines the sampling space of a carrier used in, for example, multi-phase FIG. 1 is an example of a QPSK signal constellation; phase shift keying or multi-value quadrature amplitude FIG. 2 is an example of a 16-QAM signal constella- modulation. tion; [0013] Preferably, the transmission unit transmits the 15 FIG. 3 illustrates the structure of the modulation and sampling pattern together with the hierarchically modu- demodulation device according to an embodiment lated data. of the invention; [0014] In another aspect of the invention, a demodu- FIG. 4 is a block diagram of the modulator included lation device that receives and demodulates hierarchi- in the modulation and demodulation device shown cal modulation data is provided. The demodulation de- 20 in FIG. 1; vice comprises a receiving unit that receives hierarchi- FIG. 5 is a block diagram of the demodulator includ- cal modulation data having been subjected to hierarchi- ed in the modulation and demodulation device cal modulation using multiple types of modulation tech- shown in FIG. 1; niques, and a demodulation unit that demodulates the FIG. 6 is a graph showing an example of hierarchi- hierarchical modulation data using a demodulation tech- 25 cal modulation carried out by the modulator shown nique corresponding to a specific hierarchy of the hier- in FIG. 4; archical modulation data. FIG. 7 is a table of a set of 16-QAM modulation sig- [0015] Preferably, the demodulation unit is furnished nals; with multiple types of demodulation techniques, and in FIG. 8 is a table of sampled transmission data mod- this case, the demodulation device further comprises a 30 ulated by 16-QAM; demodulation type selection unit that selects one of the FIG. 9 illustrates correlation between 16-QAM mod- demodulation techniques to be used for demodulation ulation signals and QPSK modulation signals hav- of the hierarchical modulation data. Accordingly, the hi- ing been subjected to 16-QAM/QPSK hierarchical erarchical modulation data are demodulated using the modulation; and selected one of the demodulation techniques. 35 FIG. 10 is a table of the demodulation results of [0016] The demodulation type selection unit selects 16-QAM modulation signals using the QPSK de- said one of the demodulation techniques in accordance modulation technique. with, for example, the traffic of a service area, the prop- agation environment, or a service request. DETAILED DESCRIPTION OF THE INVENTION [0017] Preferably, the receiving unit receives a sam- 40 pling pattern used for the hierarchical modulation, to- [0020] The present invention will now be described in gether with the hierarchical modulation data. In this detail in conjunction with the attached drawings. FIG. 3 case, the demodulation unit demodulates the hierarchi- illustrates a modulation and demodulation device (re- cal modulation data using the sampling pattern. ferred to as a ), which comprises a modulator [0018] With the above-described arrangements, 45 and a demodulator, according to an embodiment of the transmission data are modulated in a hierarchical man- invention. ner using multiple types of modulation techniques. The [0021] Modulation and demodulation device 100 (Mo- demodulating device on the receiving side does not dem A) and modulation and demodulation device 200 have to be furnished with all the demodulation functions (Modem B) are located at physically separate positions, corresponding to the modulation techniques on the 50 and carry out data transmission via wireless telecom- transmission side, but may have a single demodulation munications. The modulation and demodulation devices function corresponding to a specific hierarchy of the hi- 100 and 200 (Modem A and Modem B) have the same erarchical modulation data. Consequently, the received structure, and they include modulators 10, 20, and de- data are appropriately demodulated even if the modu- modulators 11, 21, respectively. Each of the modulators lation ability on the transmission side and the demodu- 55 10 and 20 modulates transmission data in a hierarchical lation ability on the receiving side are not totally consist- manner. Each of the demodulators 11 and 21 demodu- ent with each other. When the receiving side demodu- lates a received signal according to its receiving ability. lating device is furnished with two or more types of de- Since the structures of the modulation and demodula-

3 5 EP 1 406 421 A2 6 tion devices 100 and 200 are the same, the detailed the multiple modulation types include 16-QAM, which is structure thereof will be explained referring to one of an example of multi-value QAM, and QPSK, which is an these two devices, specifically, Modem A. example of multi-phase PSK. Since multiple modulation [0022] FIG. 4 illustrates the modulator 10 of the mod- techniques, namely, 16-QAM and QPSK, are used, the ulation and demodulation device 100 (Modem A) shown 5 sampling pattern generating unit 1 generates sampling in FIG. 3. patterns for 16QAM and QPSK. The sampling pattern [0023] The modulator 10 comprises a sampling pat- for 16-QAM causes the transmission data to be sampled tern generating unit 1, a modulation unit 2, and a trans- at one of sixteen possible states separated by a pre- mission unit 3. The sampling pattern generating unit 1 scribed sampling space (quantization in the amplitude generates sampling patterns according to modulation 10 direction) every sampling period (Bt). The sampling pat- types, and supplies the sampling patterns to the modu- tern for QPSK causes the transmission data to be sam- lation unit 2. The sampling pattern represents informa- pled at one of four possible states every sampling period tion about the sampling period for acquiring discrete da- (Bt). ta along the temporal axis and information about sam- [0028] FIG. 6 illustrates an example of hierarchical pling space (or interval) for acquiring discrete data (i.e., 15 modulation carried out by the modulation unit 2, which quantization) in the amplitude direction. The sampling is obtained by sampling the transmission data using a pattern generating unit 1 is capable of generating a sam- 16-QAM sampling pattern (sampling pattern 1) and a pling pattern according to a modulation type. The mod- QPSK sampling pattern (sampling pattern 2), and by ulation unit 2 converts analog transmission data into dig- modulating the sampled data. In FIG. 6, the curve A rep- ital data based on the sampling pattern supplied from 20 resents analog information (for example, voice or the sampling pattern generating unit 1, and modulates sound) as transmission data. If digital data are transmit- the sampled digital data in a hierarchical manner. The ted based on QAM modulation in which continuous an- hierarchical modulation will be explained later. The alog data are sampled at a sampling period along the transmission unit 3 converts the modulation signal of the horizontal axis (or time axis) and quantized at a sam- transmission data having been subjected to the hierar- 25 pling interval along the vertical axis, the restoration ac- chical modulation into a radio wave, and outputs the ra- curacy of the original data is improved as the sampling dio frequency transmission signal. interval along the vertical axis becomes shorter. In other [0024] FIG. 5 is a block diagram of the demodulator words, the smaller the sampling space in the amplitude 11 of the modulation and demodulation device 100 (Mo- directions, the more completely the continuous temporal dem A). 30 (analogue) signal can be restored from the sampling val- [0025] The demodulator 11 comprises a receiving unit ues. 4, a demodulation type selection unit 5, and a demodu- [0029] In FIG. 6, digital transmission data B1-B16 lation unit 6. The receiving unit 4 carries out RF process- (4-bit data) sampled and quantized based on the ing, such as frequency conversion, on the signal re- 16-QAM sampling pattern (sampling pattern 1) are rep- ceived via a transmission medium (in this example, a 35 resented by dark circles. FIG. 7 illustrates the correlation wireless network), and supplies the processed signal to between the constellation points of the 16-QAM signal the demodulation unit 6. The demodulation type selec- constellation shown in FIG. 2 and the modulation sig- tion unit 5 selects a demodulation type from the demod- nals. For the digital data B1-B16, modulation signals ulation functions (or available demodulation types) of shown in FIG. 8 are acquired from the 16-QAM signal the demodulation unit 6, and designates the demodula- 40 constellation of FIG. 2 and the correlation of FIG. 7. The tion type for the demodulation unit 6. The demodulation modulation signals correlated to the sampling data B1 unit 6 demodulates the received signal using the select- through B16 in FIG. 8 are mapped to the constellation ed demodulation type to acquire the data. points indicated by dark circles in FIG. 9. For example, [0026] In this manner, data are transmitted between the modulation signal (-0.9487-0.9487i) of 16-QAM sig- the modulation and demodulation device 100 (Modem 45 nal (1111) for sampling data B1 is mapped to constella- A) and the modulation and demodulation device 200 tion point (1111) indicated by the dark circle in the third (Modem B). Details of hierarchical modulation carried quadrant. Similarly, the modulation signal (- out on the transmission side are described below, as- 0.9487-0.3162i) of 16-QAM signal (1110) for sampling suming that signals are transmitted from the modulation data B2 is mapped to constellation point (1110) indicat- and demodulation device 100 (Modem A) to the modu- 50 ed by the dark circle in the third quadrant. The same lation and demodulation device 200 (Modem B). applies to the 16-QAM signals of B3 and the subsequent sampling data. (Operations of Modulator 10 of Modem A on [0030] Returning to FIG. 6, digital transmission data Transmission Side) (2-bit data) B1-B16 sampled and quantized based on 55 the QPSK sampling pattern (sampling pattern 2) are [0027] The modulator 10 of the transmission-side Mo- represented by white squares. Since QPSK modulation dem A carries out hierarchical modulation of transmis- uses four possible states produced by two carriers out sion data for multiple modulation types. In this example, of phase by 90 degrees, the QPSK sampling pattern

4 7 EP 1 406 421 A2 8 contains information required to sample the transmis- modulation signal via the wireless sion data at four sampling states (00, 10, 11, 01). The network, the demodulation unit 6 demodulates the re- modulation phases for these four states are indicated ceived signal as it is using the 16-QAM demodulation below. technique if the demodulator is furnished with a 16-QAM 5 demodulation function. On the other hand, if the demod- ulation unit 6 has only a QPSK modulation ability, with- (00): π/4 out being furnished with the 16-QAM demodulation function, then the received 16-QAM/QPSK hierarchical modulation signal is demodulated in the following man- (10): 3π/4 10 ner based on the QPSK modulation technique. [0035] The demodulation unit 6 determines to which quadrant the 16-QAM layer of the received signal be- (11): -3π/4 longs, and finds the corresponding QPSK state in the determined quadrant, prior to carrying out QPSK de- 15 modulation. For example, if the signal of the 16-QAM (01): -π/4 layer represents any one of the four states (0000, 0001, 0010, 0011) of the first quadrant, the modulator 6 takes [0031] When carrying out hierarchical modulation to the first two bits (00 in this example) from the bit se- these four signal states and mapping into the same co- quences of the received 16-QAM signal, and finds a sin- ordinate plane as the 16-QAM signal states, the signal 20 gle state (00) of QPSK layer mapped in the first quad- constellation shown in FIG. 9 is obtained. FIG. 9 shows rant, as indicated by the white square in FIG. 9. The de- the correlation between 16-QAM constellation points modulation unit 6 performs the same operation and suc- and QPSK constellation points during the 16-QAM/ cessively carried out QPSK demodulation for all of the QPSK hierarchical modulation performed by the modu- sampled data B1 through B16. The demodulation result lator 10. Four states (0000, 0001, 0010, 0011) of 25 of the 16-QAM modulation signal using the QPSK de- 16-QAM indicated by dark circles in the first quadrant modulation technique is shown in FIG. 10. The demod- correspond to a single state (00) in the QPSK signal ulation unit 6 outputs the QPSK demodulation results to space, which is indicated by a white square in the first the next processing stage. quadrant. This two-bit data are mapped to the modula- [0036] Since the transmission data have been modu- tion phase of π/4. 30 lated in a hierarchical manner using multiple types of [0032] Similarly, four states (1000, 1001, 1010, 1011) modulation techniques, the modulation signal can be indicated by dark circles in the second quadrant corre- demodulated on the receiving side as long as the receiv- spond to a single state (10) in the QPSK signal space, ing side demodulator has a demodulation ability corre- and this two-bit data are mapped to the modulation sponding to at least one of the multiple modulation phase of 3π/4. Four states (1100, 1101, 1110, 1111) in- 35 types. This means that even if the modulation/demodu- dicated by dark circles in the third quadrant correspond lation abilities on the transmission side and the receiving to a single state (11) in the QPSK signal space, and this side are not totally consistent with each other, transmis- two-bit data are mapped to the modulation phase of -3π/ sion data can be demodulated appropriately according 4. Finally, four states (0100, 0101, 0110, 0111) indicated to the demodulation ability of the receiving side modu- by dark circles in the fourth quadrant correspond to a 40 lator, without increasing the circuit scale. single state (01) in the QPSK signal space, and this two- [0037] In the above-described example, it is assumed bit data are mapped to the modulation phase of -π/4. that the demodulation unit 6 of the receiving side de- [0033] The data in the 16-QAM space and the data in modulator 21 has only demodulation ability for a QPSK the QPSK space are mapped in a hierarchical manner signal. However, the present invention is not limited to as a layered structure having the same coordinate axes. 45 this example. For example, the modulation unit 6 may This operation is referred to as hierarchical modulation have two or more types of demodulation functions, and of transmission data in this embodiment. the optimum demodulation type may be selected from the multiple types of demodulation techniques. In this (Operations of Demodulator 21 of Modem B on case, the demodulation type selection unit 5 shown in Receiving Side) 50 FIG. 5 is used to select the optimum demodulation type. [0038] The demodulation type selection unit 5 man- [0034] Next, the operations of the demodulator 21 of ages the demodulation ability of the demodulation unit the modulation and demodulation device 200 (Modem 6, and selects the optimum demodulation type for the B) for demodulating the 16-QAM/QPSK hierarchical demodulation unit 6, taking into account the propagation modulation signal transmitted from Modem A will be ex- 55 environment, the service request, and other factors. The plained. The demodulator 21 has the same structure as demodulation unit 6 operates in accordance with the se- demodulator 11 shown in FIG. 5. When the receiving lected demodulation type supplied from the demodula- unit 4 of the demodulator 21 receives the hierarchical tion type selection unit 5. For instance, if the demodula-

5 9 EP 1 406 421 A2 10 tion unit 6 has a 16-QAM demodulation function and a chical modulation is explained using 16-QAm and QPSK function, then the demodulation type selection QPSK. However, the present invention can be applied unit 5 selects the most appropriate one at the time of to any multi-value QAM exceeding sixteen signal states receiving the modulation signal, taking into account the (for example, 128 or 256 states), and any multi-phase traffic of the service area, the propagation environment, 5 QPSK, such as π/4-shift QPSK or BPSK. the service request, and other factors. [0043] Although, the present invention has been de- [0039] Especially, under the mobile telecommunica- scribed using a modulation and demodulation (MO- tion environment in which the on the transmis- DEM) device, providing a modulation device and a de- sion side and the receiving side are connected via a modulation device separately is also within the scope of wireless telecommunications medium, with one of the 10 the present invention. modems moving, the influence of fluctuation due to fad- [0044] Since transmission data are modulated by ing has to be taken into account when selecting the de- multiple types of modulation techniques in a hierarchical modulation type. For example, when the influence of the manner before the data are transmitted, the demodula- instantaneous fading fluctuation is large, the QPSK de- tor of the receiving side device can demodulate the re- modulation type with a smaller number of modulation 15 ceived data as long as it has at least one of the demod- signal states is generally selected, and the received da- ulation functions corresponding to a specific hierarchy ta are demodulated so as to satisfy the prescribed qual- of the multiple demodulation types. If the demodulator ity to the greatest extent possible. On the other hand, of the receiving side device has two or more types of under the propagation environment in which the influ- demodulation functions, the optimum demodulation ence of the instantaneous fading fluctuation is small, the 20 16-QAM demodulation type with a greater number of type can be selected according to the propagation modulation signal states is selected because the utiliza- tion efficiency per unit frequency is superior. In this case, the received data are demodulated aiming at higher environment or other factors. transmission quality. In this manner, even if the trans- 25 [0045] The modulation unit 2 of the modulator 10 (and mission quality is degraded due to a change in the prop- 20) can carry out hierarchical modulation. The transmis- agation environment, the optimum demodulation type is sion unit 3 of the modulator 10 (and 20) has a function selected in accordance with the current conditions. Con- of transmitting a modulation signal and a sampling pat- sequently, the telecommunications can be maintained tern. The sampling pattern generating unit 1 generates between the transmission side and the receiving side, 30 a sampling pattern for each of multiple types of modu- without interruption or disconnection. Furthermore, by lation techniques. The demodulation unit 6 of the de- selecting the demodulation type while taking the traffic modulator 11 (and 21) demodulates the hierarchical of the service area and the service request into account, modulation signal received at the receiving unit 4. The the service quality is improved. demodulation type selection unit 5 selects the optimum [0040] In the above-described embodiment, the hier- 35 demodulation type corresponding to one of the multiple archical modulation signal alone is transmitted from the types of modulation techniques. The demodulation unit modulator 10 of the modem A to the demodulator 21 of 6 can also demodulate the hierarchical modulation sig- the receiving side modem B. However, the sampling pat- nal based on the sampling pattern transmitted from the tern may also be transmitted to the modem B, together modulator 10. with the hierarchical modulation signal. In this case, the 40 [0046] In conclusion, since transmission data are demodulator 21 of the modem B can demodulate the modulated with multiple types of modulation techniques modulation signal using the sampling pattern. Accord- in a hierarchical manner, the receiving side demodulator ingly, the modulation unit 6 of the receiving side modu- can demodulate the modulation signal as long as it is lator 21 does not have to have multiple types of demod- furnished with at least a single demodulation function ulation functions, but has only a modulation function of 45 corresponding to a specific hierarchy of the modulation a specific hierarchy. signal. Even if the modulation/demodulation abilities on [0041] Although the present invention has been de- the transmission side and the receiving side are not to- scribed using an example of data transmission via a tally consistent with each other, data can be appropri- wireless telecommunication network, the present inven- ately demodulated according to the demodulation ability tion can be applied to data transmission via other trans- 50 of the receiving side demodulator, without requiring the mission media, such as a cable. When data transmis- circuit scale to be increased. When the receiving side sion is carried out via a wireless telecommunications demodulator has two or more types of demodulation network, the modulation and demodulation device 100 functions, the optimum demodulation type can be se- (Modem A) is installed in a mobile terminal, such as a lected in accordance with the circumstances, such as cellular phone, and the modulation and demodulation 55 the propagation environment. Consequently, telecom- device 200 (Modem B) is installed in a base station, for munications can be maintained without disconnection example. even if the communication quality is degraded due to [0042] In the above-described embodiment, hierar- change in propagation environment.

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[0047] This patent application is based on and claims one of the demodulation techniques to be used the benefit of the earlier filing date of Japanese Patent for demodulation of the hierarchical modulation Application No. 2002-291571 filed October 3, 2002, the data, wherein the demodulation unit demodu- entire contents of which are hereby incorporated by ref- lates the hierarchical modulation data using the erence. 5 selected one of the demodulation techniques.

7. The demodulation device according to claim 6, Claims wherein the demodulation type selection unit se- lects said one of the demodulation techniques in ac- 1. A modulation device comprising: 10 cordance with the traffic of a service area.

a modulation unit that modulates data in a hi- 8. The demodulation device according to claim 6, erarchical manner using multiple types of mod- wherein the demodulation type selection unit se- ulation techniques; and lects said one of the demodulation techniques in ac- a transmission unit that transmits the hierarchi- 15 cordance with the propagation environment. cally modulated data. 9. The demodulation device according to claim 6, 2. The modulation device according to claim 1, further wherein the demodulation type selection unit se- comprising: lects said one of the demodulation techniques in ac- 20 cordance with a service request. a sampling pattern generating unit that gener- ates a sampling pattern for each of the multiple 10. The demodulation device according to claim 5, types of modulation techniques, the sampling wherein the receiving unit receives a sampling pat- pattern defining a sampling space for quantiz- tern used for the hierarchical modulation, together ing said data in accordance with each of said 25 with the hierarchical modulation data, and the de- modulation techniques, wherein the modula- modulation unit demodulates the hierarchical mod- tion unit modulates said data in the hierarchical ulation data using the sampling pattern. manner using a digital signal sampled based on the sampling pattern. 11. A modulation method comprising the steps of: 30 3. The modulation device according to claim 2, where- modulating data in a hierarchical manner using in the sampling pattern defines the sampling space multiple types of modulation techniques to pro- of a carrier used in one of multi-phase phase shift duce hierarchical modulation data; and keying and multi-value quadrature amplitude mod- transmitting the hierarchical modulation data to ulation. 35 a demodulator of a counterpart communication device. 4. The modulation device according to claim 2, where- in the transmission unit transmits the sampling pat- 12. The modulation method according to claim 11, fur- tern, together with the hierarchically modulated da- ther comprising the step of: ta. 40 generating a sampling pattern for each of the 5. A demodulation device comprising: modulation techniques, the sampling pattern defining a sampling space for quantizing said a receiving unit that receives hierarchical mod- data in accordance with each of said modula- ulation data having been subjected to hierarchi- 45 tion techniques, wherein said data are modu- cal modulation using multiple types of modula- lated in a hierarchical manner using a digital tion techniques; and signal sampled based on the sampling pattern. a demodulation unit that demodulates the hier- archical modulation data using a demodulation 13. The modulation method according to claim 12, technique corresponding to a specific hierarchy 50 wherein the sampling pattern defines the sampling of the hierarchical modulation data. space of a carrier used in one of multi-phase phase shift keying and multi-value quadrature amplitude 6. The demodulation device according to claim 5, modulation. wherein the demodulation unit is furnished with mul- tiple types of demodulation techniques, the demod- 55 14. The modulation method according to claim 12, fur- ulation device further comprising: ther comprising the step of:

a demodulation type selection unit that selects transmitting the sampling pattern together with

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the hierarchically modulated data.

15. A demodulation method comprising the steps of:

receiving at a demodulator hierarchical modu- 5 lation data having been subjected to hierarchi- cal modulation using multiple types of modula- tion techniques; and demodulating the hierarchical modulation data using a demodulation technique corresponding 10 to a specific hierarchy of the hierarchical mod- ulation data.

16. The demodulation method according to claim 15, further comprising the step of: 15

furnishing the demodulator with multiple types of demodulation techniques; selecting one of the demodulation techniques to be used for demodulation of the hierarchical 20 modulation data, wherein the hierarchical mod- ulation data are demodulated using the select- ed one of the demodulation techniques.

17. The demodulation method according to claim 16, 25 wherein said one of the demodulation techniques is selected in accordance with the traffic of a service area.

18. The demodulation method according to claim 16, 30 wherein said one of the demodulation techniques is selected in accordance with the propagation envi- ronment.

19. The demodulation method according to claim 16, 35 wherein said one of the demodulation techniques is selected in accordance with a service request.

20. The demodulation method according to claim 15, further comprising the step of: 40

receiving a sampling pattern used for the hier- archical modulation, together with the hierar- chical modulation data, wherein the hierarchi- cal modulation data are demodulated using the 45 sampling pattern.

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