WO2007073832A1 - Procédé et dispositif destinés à communiquer des informations de diffusion incrémentielles - Google Patents

Procédé et dispositif destinés à communiquer des informations de diffusion incrémentielles Download PDF

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Publication number
WO2007073832A1
WO2007073832A1 PCT/EP2006/011628 EP2006011628W WO2007073832A1 WO 2007073832 A1 WO2007073832 A1 WO 2007073832A1 EP 2006011628 W EP2006011628 W EP 2006011628W WO 2007073832 A1 WO2007073832 A1 WO 2007073832A1
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WO
WIPO (PCT)
Prior art keywords
broadcast information
modulation scheme
information
qam
time instance
Prior art date
Application number
PCT/EP2006/011628
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English (en)
Inventor
Jacobus Cornelis Haartsen
Original Assignee
Telefonaktiebolaget Lm Ericsson (Publ)
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Filing date
Publication date
Priority claimed from EP05388118A external-priority patent/EP1804541B1/fr
Application filed by Telefonaktiebolaget Lm Ericsson (Publ) filed Critical Telefonaktiebolaget Lm Ericsson (Publ)
Priority to US12/097,513 priority Critical patent/US20090067542A1/en
Publication of WO2007073832A1 publication Critical patent/WO2007073832A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0008—Modulated-carrier systems arrangements for allowing a transmitter or receiver to use more than one type of modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0041—Arrangements at the transmitter end
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0056—Systems characterized by the type of code used
    • H04L1/0064—Concatenated codes
    • H04L1/0066—Parallel concatenated codes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0056—Systems characterized by the type of code used
    • H04L1/007—Unequal error protection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0072—Error control for data other than payload data, e.g. control data
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L2001/0092—Error control systems characterised by the topology of the transmission link
    • H04L2001/0093—Point-to-multipoint
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/30—Resource management for broadcast services
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • the invention generally relates to communications systems and, more particularly, to digital communications systems transmitting broadcast control information.
  • Broadcast channels are very important in cellular communications systems.
  • Broadcast Control Channels BCCHs
  • BCCHs Broadcast Control Channels
  • the standby behavior of a terminal is largely determined by the structure of the Broadcast Control Channel (BCCH).
  • the BCCH in other systems also typically referred to as a beacon channel
  • the terminal applies a low duty cycle transmission so that the terminal can 'sleep' for most of the time thereby reducing power consumption.
  • the terminal needs to 'wake up' and listen to the BCCH in order to check for paging messages on the paging channel (PCH) and to determine whether the current cell is still the cell to camp on (cell search).
  • PCH paging channel
  • Broadcast Traffic Channels can be supported by the network.
  • the BTCHs are used to transfer data and/or voice over the network and can be part of a cellular network, e.g. like Multimedia Broadcast and Multicast Services (MBMS) are in a Universal Mobile Telephone System (UMTS) network or they can e.g. be provided by a stand-alone infra-structure e.g. like such used for Digital Audio Broadcast (DAB), Digital Video Broadcast Terrestrial (DVB-T) and Digital Video Broadcast Handheld (DVB-H), etc.
  • DAB Digital Audio Broadcast
  • DVD-T Digital Video Broadcast Terrestrial
  • DVD-H Digital Video Broadcast Handheld
  • Broadcast channels tend to be very robust since they act as 'life lines' for the terminals to the network. They are required to support terminals both close to the base station and far away from the base station.
  • the power consumption in the terminals while receiving the broadcast information depends on a number of factors like the size of the broadcast message, the information rate on the air interface, the duty cycle of the broadcast message, etc.
  • the size of the broadcast message depends on the specific system. For the
  • BCCH it may include, among other things, the network identity, the cell (base station) identity, a list of neighboring cell identities, interface parameters (e.g. the permitted transmission power levels), synchronization information, paging information, etc.
  • the information rate is typically determined by the air interface parameters like the bandwidth, the modulation scheme, the coding scheme, and the spreading factor.
  • the duty cycle determines the overhead in the downlink transmissions from the network's point of view and the latency (in channel setup and network access) from the terminal's point of view.
  • a low duty cycle i.e. a small amount of time or length of the active part of a cycle compared to the overall time or total length of the cycle.
  • BCCH and BTCH are designed for the worst case, i.e. the performance of all terminals while receiving broadcast information is determined by the terminals located at the cell edge using the lowest information rate and/or at the smallest bandwidth. Terminals closer to the base station, terminals that can support higher data rates, and terminals that can support wider bandwidths cannot exploit these features to reduce the standby power consumption while listening to the broadcast channels.
  • Patent specification US 6,643,333 discloses a communications system where a block of N data symbols are divided into a plurality of partial blocks each partial block having Ns data symbols.
  • the Ns data symbols are allocated to sub-carries and are modulated in parallel onto these sub-carriers, where the modulation for each of the sub-carriers is carried out with at least one individual code symbol.
  • the sub-carriers are heterodyned to form a broadband carrier so that the Ns data symbols are transmitted simultaneously whereby the transmission is carried out in N/Ns successive partial blocks. If one data symbol is transmitted on a plurality of sub-carriers then frequency diversity for the data symbol is ensured making the transmission more interference resistant.
  • the number of data symbols in a partial block can be varied depending on the transmission conditions of the radio interface thereby varying the bit or information rate on the basis of transmission conditions. Further, the number of sub-carriers allocated to one data symbol can be varied depending on the transmission conditions of the radio interface thereby making it possible to match the interference immunity to the transmission conditions and manage the frequency resources economically. Power conservation of terminals is not addressed.
  • Patent specification US 5,577,087 discloses variable modulation communication where one modulation scheme, 16-Quadrature Amplitude Modulation (16-QAM), is used during communication for terminals close to the base station while another modulation scheme, Quadrature Phase Shift Keying (QPSK), is used for terminals more remote from the base station, i.e. under more noisy conditions.
  • the determination of which demodulation scheme to use is based on reception of a control signal from the base station in a given terminal during idle time and more specifically on the basis of the reception power in the given terminal.
  • a request for a given modulation scheme is then sent to the base station when communication is requested and communication with the terminal is done according to the requested modulation scheme at the terminal's allocated time slot.
  • Patent specification US 6,125,148 discloses demodulation in a communications system that supports multiple modulation schemes but using an identical demodulator where data or voice is communicated over a traffic channel using a first linear modulation scheme (e.g. 16-QAM) and where a control channel associated with the traffic channel uses a second linear modulation scheme (e.g. QPSK) for communicating associated control information. Power conservation of terminals is not addressed.
  • a first linear modulation scheme e.g. 16-QAM
  • QPSK linear modulation scheme
  • Another object is to enable more capable terminals and/or under favorable communications conditions to receive information faster while still maintaining support for terminals being less capable and/or under less favorable communications conditions.
  • a method of communicating broadcast information comprising transmitting broadcast information comprising at least two parts to at least one communications terminal, where the transmission comprises transmitting the broadcast information during at least a first time instance, and where the transmission further comprises transmitting incremental broadcast information during a time instance being different from the first time instance.
  • Incremental broadcast information is additional information that is transmitted to allow narrowband terminals or terminals under unfavorable or less favorably propagation conditions to receive the entire broadcast message correctly.
  • the beneficial use of incremental broadcast information may e.g. arise from the fact that the data/information rate is not high enough in certain terminals to accommodate all the broadcast information as fast as other terminals are capable of.
  • This can e.g. be caused by a narrow available bandwidth, i.e. only a limited available transmission bandwidth and e.g. therefore only a limited number of Orthogonal Frequency Division Multiplexing (OFDM) sub- carries.
  • OFDM Orthogonal Frequency Division Multiplexing
  • It can also be caused by a low spectral efficiency (typically expressed in number of bits/Hz), i.e. the number of bits per symbol or caused by the complexity or information rate/level of the used constellation diagram for the used encoding schemes of certain terminals.
  • forward-error-correction coding also typically referred to as incremental redundancy
  • incremental redundancy is required for error-free demodulation of the broadcast message.
  • a terminal having wide-band capability is able to receive the broadcast information more quickly, whereas the information that is sent as incremental information at a later point in time also serves the less capable or less favorable terminals.
  • a communications terminal may e.g. be a mobile phone, a Personal Digital Assistant (PDA), a PC, a Consumer Electronics (CE) device, a media-device, a TV-terminal or TV receiver communicating with a satellite or like, etc.
  • the terminal(s) can be any (stationary or portable) electronic device with wireless communication capabilities.
  • the incremental broadcast information comprises one or more selected from the group of:
  • the broadcast information comprises a number of parts wherein one part is transmitted at a first frequency range at said first time instance and wherein at least one of the other parts is transmitted at another frequency range at said first time instance, and where the at least one of the other parts is re-transmitted as incremental information at said time instance being different from the first time instance.
  • a terminal having wide band capability is able to receive the broadcast information more quickly where the information that is sent at the additional frequency ranges is sent as incremental information so that the less capable or less favorably terminals will still be able to receive the information (although at a later point in time).
  • the time instance being different from the first time instance is a time instance that is later in time than the first time instance.
  • a capable terminal may receive information it missed (e.g. due to some temporary fade or glitch) when that information is sent (again) as incremental information.
  • a systematic encoder outputs information bits as said broadcast information and a number of parity bits as said incremental broadcast information where the information bits are transmitted first followed by one or more of the parity bits. In this way, a terminal with a good signal-to-noise ratio is able to receive the broadcast information more quickly.
  • the parity bits are re-ordered by an interleaver before being transmitted. This enables randomization of the parity bits which increases the robustness in the decoding scheme.
  • a first and at least a second modulation scheme are supported during transmission and where the method comprises transmitting the broadcast information according to the first modulation scheme and transmitting the incremental broadcast information according to the second modulation scheme, where the first modulation scheme has a higher information rate than the second modulation scheme and where information transmitted in the second modulation scheme is transmitted as a part of the information in the first modulation scheme in at least one time instance.
  • the first modulation scheme is 16-QAM
  • the second modulation scheme is QPSK
  • the broadcast information has a size of 8 bits, where the broadcast information is arranged in a first block (b_0, b_1 ), a second block (b_2, b_3), a third block (b_4, b_5) and a fourth block (b_6, b_7), each of 2 bits, where
  • the first and second blocks (b_0, b_1 , b_2, b_3) are transmitted as the first symbol so that the first block (b_0, b_1 ) can be received according to both QPSK and to 16-QAM and so that the second block (b_2, b_3) can be received according to 16-QAM,
  • the third and fourth blocks (b_4, b_5, b_6, b_7) are transmitted as the second symbol so that the third block (b_4, b_5) can be received according to both QPSK and to 16-QAM and so that the fourth block (b_6, b_7) can be received according to 16-QAM
  • - the second block (b_2, b_3) is transmitted as the third symbol and is transmitted as incremental information so that it can be received according to QPSK
  • a first and at least a second modulation scheme are supported during transmission and where the method comprises transmitting the broadcast information according to the first modulation scheme and transmitting the incremental broadcast information according to the second modulation scheme, where said first modulation scheme comprises N constellation points and said second modulation scheme comprises M constellation points, where N and M are integers and M ⁇ N and where said M constellation points are a sub-constellation of the N constellation points and where information sent in the second modulation scheme is sent as a part of the information in the first modulation scheme in at least one time instance.
  • the information sent in the second modulation scheme is sent only as a part of the first modulation scheme only as long as the first modulation scheme is used (e.g. in the first and 2. symbol slot in Figure 3c).
  • constellation points of the first modulation scheme that is used for constellation points of the second modulation scheme are selected to be points that have the biggest mutual spacing. This is advantageously as there is no information left for the 16-QAM terminal(s) (so it does not matter which symbol is used as long as it is in the same Q-I quadrant), whereas these constellation points have the best distance properties thereby giving the best error tolerance.
  • a first and at least a second modulation scheme are supported during transmission and where the method comprises transmitting the broadcast information according to the first modulation scheme and transmitting the incremental broadcast information according to the at least second modulation scheme, where the first modulation scheme is selected from the group of: 16-QAM and 64-QAM and where the at least second modulation scheme is one or more selected from the group of QPSK and 16- QAM.
  • constellation points in a Q-I space are non-equidistant, where constellation points within a given cluster are substantially equidistant and where clusters of constellation points are placed further apart compared to a placement of clusters of constellation points, where all the constellation points are equidistant.
  • the clusters (a cluster being a group of symbols in one scheme representing the same symbol in the other scheme) are spaced further apart thereby improving the error rate even more than already achieved due to the merging or mapping symbols into clusters.
  • the present invention also relates to a system for communicating broadcast information, the system comprising:
  • a transmitter transmitting broadcast information comprising at least two parts to at least one communications terminal, where the transmission comprises transmitting the broadcast information during at least a first time instance, and where the transmission further comprises transmitting incremental broadcast information during a time instance being different from the first time instance.
  • the present invention also relates to a corresponding terminal and transmitter or base-station.
  • the system, terminal, and transmitter and embodiments thereof correspond to the method and embodiments thereof and have the same advantages for the same reasons.
  • the invention also relates to a computer readable medium having stored thereon instructions for causing one or more processing units to execute the method according to the present invention.
  • Figure 1 schematically illustrates a network comprising a base station and a number of terminals
  • Figure 2 schematically illustrates the use of incremental broadcast information according to one embodiment of the present invention
  • Figures 3a - 3e schematically illustrate different modulation schemes and different embodiments in order to provide different information rates to terminals within a cell;
  • Figure 4 schematically illustrates an encoder according to one embodiment, of the present invention
  • FIG. 5 schematically illustrates broadcast information parts distributed in time and frequency according to another embodiment of the present invention.
  • Figures 6a, 6b, 6c and 6d illustrate an alternative embodiment than the one primarily described in connection with Figures 3a - 3e.
  • Figure 1 schematically illustrates a network comprising a base station and a number of terminals. Shown, as an example, is a cell (100) of a communications network like GSM, EDGE in GSM, UMTS, or the like that comprises a base station (BS) (101 ) that supports a number of terminals (102, 103, 104, 105) within the cell (100).
  • BS base station
  • two terminals (T1 , T1') (102, 104) that are low- cost and/or low-complexity terminals e.g. having low or medium information rate and/or small or medium bandwidth, etc.
  • one of the terminals (T1 ) is located in near-optimal or optimal conditions (e.g. near to the base station (101 ), having favorable propagation conditions, having line-of-sight to the base station (101 ), and/or the like).
  • the other terminal (T1 1 ) of the two terminals is located in near-worst case, worst case, or less favorable conditions (e.g. relatively far away from the base station (101 ), at the cell edge, in a fading dip, and/or the like).
  • two other terminals (T2, 12') (103, 105) that are more advanced e.g. capable of high(er) information rate, high(er) bandwidth, and/or the like
  • one of the terminals (T2) is located in near- optimal or optimal conditions (e.g. near to the base station (101 ), having favorable propagation conditions, having line-of-sight to the base station (101 ), and/or the like as T1 above).
  • the other terminal (T2 1 ) of the two advanced terminals is located in near-worst case, worst case, or less favorable conditions (e.g. relatively far away from the base station (101 ), at the cell edge, in a fading dip, and/or the like as TT).
  • the broadcast control channel (BCCH) and the broadcast traffic channel (BTCH) are designed to accommodate the worst case whereby more advanced terminals and/or terminals located in more optimal situations can not resume their 'sleep' state conserving power faster than the terminals under the worst case situations or having more limited capabilities.
  • broadcast information e.g. for a BCCH and/or a BTCH is provided that enables more advanced terminals (like terminal T2 and T2') and/or terminals located in more optimal situations (like terminal T1 and T2) than the worst case to optimize their power consumption during standby (BCCH) or when listening to a broadcast traffic channel (BTCH).
  • BCCH standby
  • BTCH broadcast traffic channel
  • the first increment or increments will be sufficient for more capable terminals or more favorably placed terminals to decode the broadcast message. Additional increments sent at a later point in time
  • FIG. 2 schematically illustrates the use of incremental broadcast information according to one embodiment of the present invention. Shown is broadcast information (200), e.g. in the form of a broadcast message, that is sent incrementally in a number of consecutive slots or symbols (201 , ..., 204) at different points in time.
  • broadcast information e.g. in the form of a broadcast message
  • a high rate broadcast message is e.g. sent which contains all the information needed for a terminal that is close to the base station of the cell (e.g. T1 and T2 in Figure 1 ) and thereby can do without channel coding and/or for a terminal that supports higher modulation schemes (e.g. T2 and T2' in Figure 1 ) and thereby can receive more information during each slot or symbol.
  • the first symbol or slot also contains part of the broadcast message required for the terminals (e.g. T1 ' and T2' in Figure 1 ) that need channel coding and/or cannot support the higher modulation schemes (e.g.
  • T1 and T1 ' in Figure 1 so they can benefit some from the information sent in the first slot or symbol.
  • this information is located in the part that can be received by terminals only supporting lower modulation schemes.
  • incremental broadcast information (205) is present in the second slot or symbol (202) (and even in additional slots or symbols (203, 7) if necessary).
  • a broadcast message consist of parts 'A', 'B', 'C and 'D'.
  • the broadcast message may e.g. be sent with 'A' in the first time slot or symbol, 'B' in the second, 1 C in the third and 'D' in the last.
  • 'C could be sent in the first time slot or symbol together with 'A' and 'D' could be sent in the second time slot or symbol together with 'B'.
  • Only the advanced or favorably located terminals will be able to extract message parts 'C and 'D' in the first and second time slots or symbols in addition to the conventional parts 'A' and 'B'.
  • Conventional or worst case terminals will only be able to extract 'A' and 'B' from the first and second time slots or symbols.
  • Various other orderings may be just as applicable, e.g. 'A', 'C, 'B', 'D' sent during the four time slots or symbols and 'B' and 'D' sent in the first two time slot or symbols, etc. As long as the ordering is consistent and well known for the terminals.
  • the incremental information can e.g. in Time Division Multiple Access (TDMA) systems be sent at other slots or symbols than the ordinary broadcast information, i.e. at a later time instance.
  • TDMA Time Division Multiple Access
  • advanced terminals e.g. capable of receiving information at a high information rate
  • terminals under favorable propagation conditions e.g. close to the base station only have to receive this first slot or symbol (201) before they can resume their 'sleep' state and being conserving power. This is done without having to wait for the less capable (e.g. due to placement and/or capabilities) terminals as would be the case if the sending of broadcast information was designed to accommodate the worst or worse case situation(s).
  • the less capable terminals receive the needed broadcast information during later slots or symbols as incremental broadcast information.
  • bit streams are sent in parallel over a set of sub-carriers, each sub- carrier supporting a bit stream.
  • the set of sub-carriers may for instance span a total bandwidth of 1.25 MHz. If each set, as an example, contain 100 sub- carriers and the operator has been allocated 5 MHz there is room for 4 complete sets or 400 sub-carriers. However, another operator that has been allocated 15 MHz has room for 12 sets or 1200 sub-carriers.
  • the broadcast channel needs to be dimensioned for 1.25 MHz.
  • Terminals that operate in the 1.25 MHz bandwidth may require several OFDM symbols in order to receive the entire broadcast message.
  • a single symbol may contain the entire broadcast message as it can accommodate four times as much information per symbol compared to when only the three additional sub-carriers are used.
  • a first part of the broadcast information is transmitted at a first frequency band (i.e. the first 100 sub-carriers in the example above), a second part of the broadcast information is transmitted at a second frequency band (i.e. the next 100 sub-carriers), and so on until all the broadcast information has been sent or all the available sets have been used. It has to be assured that the rest of information is sent to the terminals that only operate in the more limited frequency band at the next time instant(s). This is illustrated and explained in greater detail in connection with Figure 5.
  • terminals that have wideband capabilities will receive the broadcast information sooner and will therefore be able to enter their 'sleep' mode earlier thereby conserving additional power.
  • Figures 3a, 3b and 3c schematically illustrates different modulation schemes in order to provide different information rates to terminals within a cell.
  • a communications system supports different modulation schemes in order to provide different information rates to terminals within a cell.
  • a system is considered that uses QPSK (Quadrature Phase Shift Keying) modulation but where it is extended with a 16-QAM (Quadrature Amplitude Modulation) mode in order to double the data or information rate.
  • QPSK Quadrature Phase Shift Keying
  • 16-QAM Quadrature Amplitude Modulation
  • the broadcast control channels would all use QPSK, whereas only a dedicated (traffic) channel could apply 16-QAM.
  • the broadcast channel is changed in such a way that it supports both QPSK transceivers (i.e. old or medium or low-tech terminals and/or terminals at the cell edge; e.g. T1 , TT and T2' in Figure 1 ) and 16-QAM transceivers (i.e. more advanced terminals capable of a high(er) bit or information rate and located nearer the base station; e.g. T2 in Figure 1 ).
  • QPSK transceivers i.e. old or medium or low-tech terminals and/or terminals at the cell edge; e.g. T1 , TT and T2' in Figure 1
  • 16-QAM transceivers i.e. more advanced terminals capable of a high(er) bit or information rate and located nearer the base station; e.g. T2 in Figure 1 .
  • the broadcast information has a size of 8 bits. Since 2 bits pr. symbol can be sent in the QPSK then 4 symbols are needed for a QPS
  • the 8-bit broadcast information is represented by bits b_0, b_1 , ..., b_7.
  • Bit b_0 is sent first.
  • For a QPSK terminal it is required to map (b_0, b_1 ) to the first symbol, (b_2, b_3) to the second symbol, (b_4, b_5) to the third symbol and (b_6, b_7) to the fourth symbol as a QPSK terminal can only receive 2 bits pr. symbol.
  • a 16-QAM terminal it is required to map (b_0, b_1 , b_2, b_3) to the first symbol and (b_4, b_5, b_6, b_7,) to the second symbol as a 16-QAM terminal can receive 4 bits pr. symbol.
  • the first symbol for QPSK and the first symbol for 16-QAM must be one and the same symbol.
  • the second symbol for QPSK and the second symbol for 16-QAM must be one and the same symbol. This is achieved by using the constellation diagrams as shown in Figures 3a and 3b resulting in the ordering as shown in Figure 3c.
  • T and 'Q' values in the intervals as given by hatched boxes (310) represents the value '0001'.
  • the same 'I' and 'Q' values would according to the QPSK scheme give the value '00', as can be seen from Figure 3b.
  • a 16-QAM capable terminal would receive '0001 ' by receiving T, 'Q' values (310) while a QPSK capable terminal would receive O' for the same 'I', 'Q' values.
  • the specific size of the intervals may vary according to the specific implementation.
  • the first symbol shall contain b_0 and b_1 for both the QPSK terminal(s) and the 16-QAM terminal(s).
  • the first symbol shall also contain b_2 and b_3 for the 16-QAM terminal(s). If the constellation points are represented by b_A, b_B, b_C, and b_D, then b_0 shall be mapped to b_A, while b_1 to b_B, b_2 to b_C, and finally b_3 to b_D.
  • the second symbol shall contain b_4 and b_5 for both the QPSK terminal(s) and the 16-QAM terminal(s) and it shall also contain b_6 and b_7 for the 16-QAM terminal(s).
  • b_4 shall be mapped to b_A, while b_5 to b_B, b_6 to b_C, and finally b_7 to b_D.
  • the 16-QAM terminal(s) can receive all 8 bits within two symbols only.
  • the third symbol shall contain b_2 and b_3 for the QPSK terminal(s), while the fourth symbol shall contain b_6 and b_7 also for the QPSK terminal(s) being transmitted as incremental information (205).
  • Figure 3c for an overview of the above-mentioned ordering of the bits in the symbols for this particular example.
  • mapping provides the correct bit order for the 16-QAM receiver, whereas the QPSK receiver has to do some bit reordering in order to get to the correct message.
  • An alternative mapping could have the correct order for the QPSK receiver and a reordering requirement for the 16-QAM receiver.
  • (b_0, b_1 ), (b_2, b_3), (b_4, b_5), and (b_6, b_7) are mapped to (b_A , b_B) in the first, second, third and fourth symbols, respectively.
  • (b_4, b_5) are mapped to (b_C, b_D) in the first symbol
  • (b_6, b_7) are mapped to (b_C, b_D) in the second symbol.
  • the extra bits for the QPSK terminal(s) may be sent as incremental broadcast information incremented in time.
  • the first symbol should be the constellation point '1010' in Figure 3a. This point would be interpreted as '1010' in a 16-QAM terminal while being interpreted as '10' in a QPSK terminal.
  • the constellation points '0011 ', '1011 ', '1111 ', and '0111 ' shall be used by the transmitter as there is no information left for the 16-QAM terminal(s), whereas these constellation points have the best distance properties.
  • broadcast information having a size of 8 bits and the modulation schemes 16-QAM and QPSK are used, other embodiments are equally applicable.
  • the two modulation schemes 16-QAM and QPSK were used (as an example) where the QPSK symbols can be derived from the 16-QAM constellation by merging or mapping a cluster of four 16- QAM symbols to a single QPSK symbol.
  • a 64- QAM scheme can be used (in addition to or instead of 16-QAM and/or QPSK) as explained in connection with Figures 6a - 6d.
  • Figures 3d and 3e schematically illustrate an alternative embodiment of the one primarily described in connection with Figures 3a - 3c.
  • the constellation points are equidistant in the embodiment explained in connection with Figures 3a and 3b.
  • This is not as error robust when 16-QAM and QPSK symbols are carried simultaneously as it otherwise could be.
  • the 16-QAM symbols 1 OOOO', '0001 ', '0010', and '0011 ' all signify the same QPSK symbol, namely '00.
  • the 16-QAM symbol '0000' is selected to convey the QPSK symbol OO' then '0000' is closer to its neighbors representing other QPSK symbols (and thus more vulnerable for errors) than if '0011 ' was selected.
  • the clusters are spaced further apart thereby improving the error rate for the QPSK even more than already achieved due to the merging or mapping symbols into clusters.
  • the distance to its neighbors representing other QPSK symbols has been increased increasing the robustness further.
  • points that have the biggest mutual spacing should be selected.
  • Figure 4 schematically illustrates an encoder according to one embodiment, of the present invention. Shown, as an example, is a 1/3-rate turbo encoder (400) like one used in UMTS.
  • the encoder produces a systematic code.
  • a systematic code is a code in which the information bits to be sent and the parity bits are clearly distinguishable.
  • the encoder (400) comprises a first encoder (401 ) receiving the information bits (Inf. Bit), and a second encoder (402) receiving the information bits that have been reordered by an interleaver (403).
  • the reordering by interleaver (403) is part of the standard encoding scheme and plays a part in giving a boost of the Turbo code as generally known in the art.
  • the first encoder (401 ) produces a first parity bit P1 and the second encoder (402) produces a second parity bit P2 for each information bit (Inf. Bit).
  • Such encoders are also well known in the art.
  • the ordering of the set of parity bits P1 and the ordering of the set of parity bits P2 are randomized by a randomizer, (additional) interleaver, or the like (404) (performing pseudo-random permutation).
  • a randomizer additional interleaver, or the like (404) (performing pseudo-random permutation).
  • the positions of the punctured bits are randomized, which makes the decoding process more robust.
  • the encoder (400) receives and stores an information bit (Inf. Bit) and its associated parity bits (P1 , P2) at each time instance e.g. by an accumulator or the like (not shown).
  • the additional interleaver (404) After a number of bits have been stored (e.g. 100 bits) in the encoder (400) then the additional interleaver (404) generates a bit-stream of first the 100 information bits (Inf. Bit) and then 100 P1 -bits followed by 100 P2-bits. After these bits have been sent, further bits are collected and the procedure repeats. In this way, favorable terminals just have to listen to the first 100 bits while non-favorable terminals have to listen to at least a part of the parity bits.
  • the present invention is equally applicable to a conventional encoder with systematic coding, i.e. without the additional interleaver (404). For these, virtual puncturing can also be assumed for the parity bits (P1 , P2) that are not received.
  • terminals with good SNR are allowed to receive only the minimum amount of information before they can return to their 'sleep' state since they do not need any or some of the parity bits (P1 and P2) due to a proper placement and simple re-arrangement of the channel coding bits, i.e. all S's before P1 s and P2s.
  • Bit pairs (b_2,b_3) and (b_6,b_7) can represent parity bits for the FEC coding.
  • Advanced receivers can extract the parity bits from the first and second symbols, whereas conventional receivers will extract these bits from the third and fourth symbols.
  • Figure 5 schematically illustrates broadcast message segments distributed in time and frequency according to another embodiment of the present invention.
  • certain terminals e.g. in an OFDM system, may benefit from the broadcast information being sent at various frequencies at the same time instance (even though not all terminals may be capable of this).
  • T2 and T2' in Figure 1 may use 1200 sub-carriers.
  • one symbol (or slot) of information with 100 sub-carriers can contain a third of the broadcast information.
  • three consecutive symbols are required to receive the entire broadcast information.
  • a 2.5 MHz wide system with 200 sub-carriers per symbol will only require two symbols.
  • a system with a bandwidth equal to or larger than 300 sub-carriers will only need a single symbol.
  • the broadcast information is split up into, as an example, three parts A, B and C and part A is sent in the first set of 100 sub-carriers, i.e. in the first frequency segment, in the first symbol, part B is sent in second set of 100 sub-carriers, i.e. in the second frequency segment, in the first symbol, and part C is sent in the third set of 100 sub- carriers, i.e. in the third frequency segment in the first symbol. Further, part B is sent (again) in the first set of 100 sub-carriers, i.e. in the first frequency segment, in the second symbol and part C is sent (again) in the second set of 100 sub-carriers, i.e. in the second frequency segment, in the second symbol. Finally, part C is sent (once again) in the first set of 100 sub-carriers, i.e. in the first frequency segment, in the first symbol.
  • wider band terminals (like T2 and T2' in Figure 1 ) will need to listen for a shorter time window in order receive the entire broadcast information and can go into 'sleep' mode sooner thereby conserving power.
  • Figures 6a, 6b and 6c illustrate an alternative embodiment than the one primarily described in connection with Figures 3a - 3c.
  • a 64-QAM scheme is used (in addition to or instead of 16-QAM and/or QPSK) where merging, grouping or mapping clusters of four 64-QAM symbols (see Figure 6a for all the 64-QAM symbols) into a cluster will give a 16-QAM scheme (see Figure 6b) and where merging, grouping or mapping clusters of four 16-QAM symbols will give a QPSK scheme (being the same as sixteen 64-QAM symbols being mapped to a QPSK symbol) (see Figure 6c).
  • Embodiments may support two or more of 64-QAM, 16-QAM, QPSK and other schemes, i.e. certain terminals being supported by a base station could receive information according to the 64-QAM scheme, where other terminals could receive information according to the 16-QAM scheme and where yet other terminals could only receive information to the QPSK scheme. In this way, even though a same 'Q' T pair is sent and received by all these types of different terminals they will obtain a different amount of information according to their scheme.
  • the same principles may be applied to even more complex constellation diagrams like 128-QAM, 256-QAM, etc.
  • a first and at least a second modulation scheme may be supported, where the first modulation scheme comprises N constellation points and said second modulation scheme comprises M constellation points, where N and M are integers and M ⁇ N and where said M constellation points are a sub- constellation of the N constellation points.
  • Figure 6d summarizes the various groupings or clusters of the different schemes.
  • the broken boxes surrounding the constellation points indicate the 'Q'-T intervals for each bit value corresponding to the hatched boxes in Figures 3a - 3e.
  • the constellation points in the original 64-QAM scheme do not show a constant inter-spacing distance. Usage of the constellation for less dense modulation scheme will then have less impact on the robustness of the less dense modulation scheme, as also explained in connection with Figures 3d and 3e.
  • any reference signs placed between parentheses shall not be constructed as limiting the claim.
  • the word “comprising” does not exclude the presence of elements or steps other than those listed in a claim.
  • the word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un système, des terminaux et un procédé destinés à communiquer des informations de diffusion, et consistant à transmettre des informations de diffusion (200) comprenant au moins deux parties à au moins un terminal de communication (T1, T2, T1', T2'). La transmission consiste à transmettre les informations de diffusion (200) pendant au moins une première instance temporelle, la transmission consistant en outre à transmettre des informations de diffusion incrémentielles (205) pendant une instance temporelle différente de la première instance temporelle. De cette manière, l'envoi des informations de diffusion en incréments, c'est-à-dire de manière incrémentielle, permet de garantir que les terminaux qui en sont capables (qui présentent de meilleures capacités, telles qu'un débit d'informations supérieur, une bande passante supérieure, etc., et/ou un meilleur emplacement, tel que le voisinage de la station de base, et qui disposent de conditions de propagation favorables, d'une visibilité directe par rapport à la station de base, etc.) recevront les informations de diffusion plus rapidement, et que, par voie de conséquence, ils pourront revenir plus rapidement à un état de 'sommeil' (à moins qu'ils doivent intervenir de manière active sur les informations de diffusion reçues) sans être limités par un ou plusieurs terminaux moins complexes ou moins performants dans les états les plus défavorables, comme ce serait le cas si l'envoi d'informations de diffusion était destiné à s'adapter aux cas les plus défavorables. Cela permet d'économiser de l'énergie pour les terminaux plus performants et/ou mieux situés étant donné que l'émetteur-récepteur est actif pendant une durée plus courte pour la réception d'une même quantité d'informations de diffusion.
PCT/EP2006/011628 2005-12-27 2006-12-05 Procédé et dispositif destinés à communiquer des informations de diffusion incrémentielles WO2007073832A1 (fr)

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US12/097,513 US20090067542A1 (en) 2005-12-27 2006-12-05 Method and Device for Communicating Incremental Broadcast Information

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EP05388118.1 2005-12-27
EP05388118A EP1804541B1 (fr) 2005-12-27 2005-12-27 Procédé, système, dispositif et support lisible sur ordinateur de communication d'informations incrémentièlles de diffusion
US75432905P 2005-12-29 2005-12-29
US60/754,329 2005-12-29

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5404355A (en) * 1992-10-05 1995-04-04 Ericsson Ge Mobile Communications, Inc. Method for transmitting broadcast information in a digital control channel
US5577087A (en) * 1991-10-31 1996-11-19 Nec Corporation Variable modulation communication method and system
US6125148A (en) * 1997-08-29 2000-09-26 Telefonaktiebolaget Lm Ericsson Method for demodulating information in a communication system that supports multiple modulation schemes
US6643333B1 (en) * 1997-03-26 2003-11-04 Siemens Aktiengesellschaft Method and transmitting device for transmitting data symbols from subscriber signals via a radio interface of a mobile communications system
US20050113087A1 (en) * 2003-11-25 2005-05-26 Rick Roland R. Early decoding of a control channel in a wireless communication system

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5577087A (en) * 1991-10-31 1996-11-19 Nec Corporation Variable modulation communication method and system
US5404355A (en) * 1992-10-05 1995-04-04 Ericsson Ge Mobile Communications, Inc. Method for transmitting broadcast information in a digital control channel
US6643333B1 (en) * 1997-03-26 2003-11-04 Siemens Aktiengesellschaft Method and transmitting device for transmitting data symbols from subscriber signals via a radio interface of a mobile communications system
US6125148A (en) * 1997-08-29 2000-09-26 Telefonaktiebolaget Lm Ericsson Method for demodulating information in a communication system that supports multiple modulation schemes
US20050113087A1 (en) * 2003-11-25 2005-05-26 Rick Roland R. Early decoding of a control channel in a wireless communication system

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