Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
  • H04B1/69—Spread spectrum techniques
  • H04B1/7163—Spread spectrum techniques using impulse radio
  • H04B1/7176—Data mapping, e.g. modulation

Definitions

• the invention relates generally to mobile communication networks. More particularly, the invention relates to transmission of data in ultra wide- band communication networks.
• Ultra wideband representing pulse-based wireless short range networks
• UWB Ultra wideband
• the UWB uses a large portion of the available bandwidth but applies low energy level. Thus, the interference caused to other physical layer transmissions is not severe.
• UWB is defined as a transmission for which a fractional bandwidth is greater than 20 %, or that the bandwidth of the transmitted signal is more than 500MHz, whichever is less, wherein each pulse in the UWB occupies the entire bandwidth.
• IEEE 802.15.4a 2007 by IEEE 802.15.4a.
• the IEEE 802.15.4a standard determines for example the physical layer and the media access control for the low-rate wireless personal area networks. The standard also determines the number of burst positions, data rate, burst duration, modulation methods, channel coding, etc.
• Embodiments of the invention seek to improve the data communica- tion in the UWB communication networks.
• an apparatus comprising processing means for performing any of the embodiments as described in the appended claims.
• Embodiments of the invention are defined in the dependent claims.
• Figure 1 presents a UWB communication network according to an embodiment
• Figure 2 shows a physical layer UWB symbol structure, according to an embodiment
• Figure 3 shows how information is indicated according to an embod- iment when applying the UWB physical layer symbol structure
• Figure 4 illustrates indication of information to different users, according to an embodiment
• Figure 5 presents indication of information to same users, according to an embodiment
• Figure 6 depicts indication of information over plurality of symbol time intervals, according to an embodiment
• Figure 7 illustrates a signaling flow diagram, according to an embodiment
• Figure 8 shows an apparatus capable of performing the embodi- ments of the invention, according to an embodiment
• Figure 9 illustrates a method according to an embodiment
• Figure 10 illustrates a method according to an embodiment.
• Radio communication networks such as the global system for mobile communications (GSM), the Long Term Evolution (LTE) or the LTE- Advanced (LTE-A) of the 3 rd Generation Partnership Project (3GPP), are typically composed of at least one base station (also called a base transceiver station, a radio network controller, a Node B, or an evolved Node B, for example), at least one user equipment (UE) (also called a user terminal, terminal device or a mobile station, for example) and optional network elements that provide the interconnection towards the core network.
• the base station connects the UEs via the so-called radio interface to the network.
• the base station may provide radio coverage to a cell, control radio resource allocation, perform data and control signaling, etc.
• the cell may be a macrocell, a microcell, or any other type of cell where radio coverage is present.
• a base station may be configured to provide communication services according to at least one of the following radio access technologies (RATs): Worldwide Interoperability for Microwave Access (WiMAX), Glob- al System for Mobile communications (GSM, 2G), GSM EDGE radio access Network (GERAN), General Packet Radio Service (GRPS), Universal Mobile Telecommunication System (UMTS, 3G) based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), LTE, LTE-A, UWB, multiband UWB, for example.
• RATs radio access technologies: Worldwide Interoperability for Microwave Access (WiMAX), Glob- al System for Mobile communications (GSM, 2G), GSM EDGE radio access Network (GERAN), General Packet Radio Service (GRPS), Universal Mobile Telecommunication System (UMTS, 3G) based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), LTE, LTE-A, UWB, multiband UWB
• the UWB as one form of an impulse radio (IR), is seen as a carrier- less baseband transmission.
• the absence of a carrier frequency differentiates impulse radio transmissions from narrow-band applications, for example.
• the UWB transmitter produces a very short time domain pulse, which is able to propagate without the need for an addi- tional RF (radio frequency) mixing stage.
• the UWB is based on discontinuous emission of very short Gaussian pulses or other types of pulse waveforms.
• the used waveform affects the selection of a modulation method for the data to be transmitted, for example. Interference caused by other transmission techniques to the UWB receiver may not be severe, as the receiver needs to listen to the channel only during the short period of time when the short pulse is received.
• the moment when the receiver is to listen to the channel may be known from information, such as beacon(s), transmitted by a system coordinator.
• a coordinator may be a personal area network (PAN) coordinator, for example.
• PAN personal area network
• the moment when to transmit, and hence to receive, may be deter- mined by spreading code.
• the spreading code may be broadcasted in the beacon, for example.
• the coordinator may manage the synchronization in the MAC (medium access control) level. However, when such beacon-enabled mode is not supported, the coordinator may be polled for synchronization data.
• the data obtained by polling or in beacons may also comprise infor- mation related to a contention free period and to a contention access period, which may be of use when defining the time to transmit and the time to listen, as known by a skilled person.
• the users may try to access the channel based on ALOHA protocol, for example.
• Figure 1 shows a communication network applying the UWB, according to an embodiment.
• the communication network may comprise a base station 102.
• the base station 102 may provide radio coverage to a cell 100 by applying the UWB radio communication protocol, control radio resource allocation, perform data and control signaling, etc.
• the cell 100 may have a short range depending on the coverage area of the UWB transmission. Further, the cell 100 may be of any size or form, depending on the antenna system utilized.
• the base station 102 may be seen as one communication point of the network.
• the base station 102 may be node B, evolved node B (eNB) as in LTE-A, a radio network controller (RNC), or any other apparatus equipped with means for being capable of transmitting and/or receiving UWB based data communication, controlling radio communication and managing radio resources within the cell 100.
• the base station 102 may establish a connection with a user equipment (UE) 104A to 104C, such as a mobile user terminal, a palm computer, or any other apparatus capable of operating in a mobile communication network and transmitting and/or receiving UWB transmission. That is, the UE 104A to 104C may perform impulse radio based data communication with the eNB 102.
• the embodiments may also take place between the network coordinators, for example.
• Figure 2 shows a symbol structure according to an embodiment of the invention.
• the symbol structure is based on the IEEE 802.15.4a standard for the UWB impulse radio.
• the UWB information is transmitted by generating radio energy at specific time instants and occupying large bandwidth.
• Each symbol may consist of an integer number of possible chips, i.e. pulses.
• the impulse radio UWB signal (representing at least one bit within the symbol time interval) is composed of a train of very short pulses.
• the pulse waveform may follow a Gaussian waveform, for example.
• the concatenated pulses define information for at least one bit in the UWB signal.
• the duration T c may be of the order of 2 ns, for example, although other lengths are possible.
• each symbol time interval T SYM is divided into two intervals 208 and 210, each with a duration T SYM /2, which enables a pulse position modulation (PPM), also known as burst position modulation (BPM).
• PPM pulse position modulation
• BPM burst position modulation
• the time interval of 208 and 210 may be called a burst position modulation interval TBPM-
• TBPM- burst position modulation interval
• a single burst event for one user shall be transmitted within the symbol time interval 200, either in the first half 208 or in the second half 210.
• interval shall contain a burst, while the second half of the selected TBPM 208 or 210 is reserved for a guard time (shown in left leaning diagonal lines).
• the available time slot for the burst is shown with reference numerals 212 and 214, while the respective guard times are shown with reference numerals 216 and 218.
• the guard time occupies half of the TBPM duration 208 or 210.
• a modulation scheme is applied to a series of UWB pulses.
• PPM pulse position modulation
• BPM burst position modulation
• the UWB PHY symbol in the prior art is capable of carrying two bits of information: Firstly, the location of the burst in either the first half 208 or the second half 210 of the symbol time interval 200 indicates one bit of information. In other words, a burst is transmitted On time', or delayed by a certain quantity, depending on whether a '1 ' or a '0' is transmitted.
• the phase of the burst (either -1 or +1 ) may be used to indicate a second bit of information.
• the second bit modulates the used pulse waveform(s) by applying a secondary modulation method.
• the information can also be imparted (modulated) on the UWB signals (pulses) by encoding the polarity of the pulse.
• the receiver then first demodulates the received data by using the PPM and then the binary phase modula- tion. This modulation method specified in the standard may be denoted as PPM+BPSK modulation.
• Selection of a specific burst time slot 202A to 202D and 202E to 202H when data is to be transmitted may depend on which UE is the intended receiver of the data, for example. That is, the bursts 202A to 202D and 202E to 202H may be reserved for different users (UEs). For example, the burst time slots 202C and 202G may be reserved for the same UE 104A of Figure 1 thus forming a pair of burst time intervals.
• the burst is transmitted in the burst time interval 202C and the burst time interval 202G (or the specific burst time interval 202E to 202H which is reserved for the UE 104A within time period 210) is empty.
• the burst is transmitted in time slot 202C and the corresponding time slot 202G representing the opposite bit value is empty, although noise may be present also on this time slot 202G as shown with reference numerals 207.
• the burst time interval 202C is empty and a burst is transmitted in the time slot 202G.
• Figure 2 shows only four burst time slots per symbol half 208 or 210, representing, for exam- pie, four users to be time multiplexed in the UWB system, the number of burst time intervals, and hence the number of maximum possible users, may be more. In an embodiment, the number of burst time intervals in each TBPM is eight. Four in Figure 2 is selected only for the sake of clarity of the Figure.
• each pulse is placed inside a slot 202A to 202D and 202E to 202H of duration T BURST positioned inside the symbol period 200 T SYM , followed by a guard time 216 or 218.
• the symbol time duration 200 may thus be divided into four quarters, from which the first quarter 212 and the third quarter 214 are intended for user data transmission according to the PPM (although only one quarter at a time), and the second quarter 216 and the fourth quarter 218 are reserved for the guard times.
• the slot position at a given time for each UE may be determined according to a specific time hopping code which may be unique to each user (centralized system) or selected randomly by each user (uncoordinated system).
• each symbol time interval 200 As only one half, either 208 or 210, of each symbol time interval 200 is utilized, the radio resources are not efficiently applied in the prior art solutions.
• the standard presented in the IEEE 802.15.4a also determines the number of burst positions for different target data rates.
• the reliability of the system may be increased in prior art solutions by increasing the duration of the burst and/or applying channel coding, such as convolutional codes.
• ultra wideband (UWB) communication technique is applied in communication of data between a transmitter (such as a base station) and a receiver (such as user equipment), wherein the UWB applies a physical layer symbol structure suitable for the application of a pulse position modulation.
• UWB ultra wideband
• Such symbol structure is shown in Figure 2 and detailed in the IEEE 802.15.4a standard. This ensures that the proposed solution is backward compatible with the technique applying the symbol structure presented in the standard.
• the UWB applies an UWB symbol structure according to the IEEE 802.15.4a standard.
• first burst time interval for example, one of time intervals 202A to 202D
• second burst time interval for example, one of time intervals 202E to 202H
• the first burst time interval one of 202A to 202D
• a bit value such as "0" or "1 ”
• a second burst time interval one of 202E to 202H
• an opposite bit value such as "1 " or "0”
• the proposed solution takes the symbol structure advantageously more efficiently in use by indicating information in each of the first and second burst time intervals. Therefore, the proposed solution does not apply the (available) burst position modulation in the pair of first and second burst time intervals.
• the proposed solution may be ap- plied for the user data that is transmitted to the receiver, for example.
• the first burst time interval and the second burst time interval which represents the opposite bit value in the PPM, form a pair of burst intervals, from which one would be empty if the PPM is applied.
• Figure 3 illustrates the proposed solution.
• Figure 3 applies the same notations as Figure 2 as far as the elements referred are the same.
• the transmitted burst may be composed of at least one pulse (chip) 304A to 304C, each having a chip duration 306.
• the chip duration 306 and the number of chips 304A to 304C concate- nated to indicate the UWB signal to the receiver may be different from the corresponding numerals with respect to the burst time slot 202C.
• the applied waveform may be different between the time slots 202C and 202G.
• the burst time intervals 202C and 202G are intended for the same single user if the pulse position modulation were applied, thus they form the pair of burst time intervals in the pulse position modulation.
• the receiver is allocated certain burst time slots when data is transmitted to the UE. Contrary to the proposed embodiment, one of these would be empty had the pulse position modulation been applied as is the case in prior art.
• Causing indication of a distinct information unit comprises in one embodiment transmission of a data burst, which data burst indicates information to the receiver.
• the data burst may be modulated, not with the burst position modulation, but with another modulation method, such as with at least one of the following: on/off keying, pulse shape modulation, pulse amplitude modulation, pulse phase modulation, and differential phase shift keying. Therefore, the receiver may obtain an information unit, such as at least one information bit, in each of the burst time slots 202C and 202G.
• the burst time interval 202C and 202G may comprise an actual transmission of a data burst, modulated with an appropriate method.
• the indication of distinct information unit may be obtained by the receiver even without actual transmission of data burst. This is because according to on/off keying, the receiver obtains indication of bit "1 ", for example, when there is transmission in the burst time interval. When there is no transmission in the burst time interval, the receiver obtains indication of a bit "0", for example.
• the receiver may obtain two bits of information during one symbol time interval 200 even without any user data being transmitted during the burst time intervals. In that case, the receiver may obtain information that a bit combination "00" is indicated, for example.
• the indication of the distinct information unit in each burst time interval is caused by transmitting a data burst in each burst time interval, wherein the burst comprises at least one pulse waveform.
• the indication of the distinct information unit in each burst time interval is caused by not transmitting anything in a specific burst time in- terval. The latter embodiment may apply the on/off keying modulation, for example.
• the distinct information unit means that the information unit in each of the burst time intervals is different information from the other burst time intervals, although the information units may, in case of diversity, represent the same data.
• the same information unit is indicated in both of the PPM burst time intervals: the first interval having transmission indicates bit "1 " and the other, not having any transmission, indicates the same information unit. In other words, from the receiver's point of view, the same information is obtained twice even though the data is received only once.
• the receiver obtains distinct information in each of the burst time intervals allocated for the receiver.
• the information unit may be at least one information bit, for example.
• the at least one bit may be indicated in the data burst or lack of data burst, for example. Indicating one bit may be the most often applied scenario due to lower requirements regarding the receiver complexity as polarity based receiver techniques are relatively simple to construct. However, indication of two or more bits may be possible with more complex receiver structures and more complex modulation methods, such as a quadrature phase shift keying (QPSK) or 8-PSK, for example.
• QPSK quadrature phase shift keying
• 8-PSK for example.
• the pulse position modulation being non-coherent modulation method provides reduced performance compared to coherent modulation methods, such as the phase modulation.
• coherent modulation methods such as the phase modulation.
• the efficiency of the data communication network may be increased.
• the whole symbol time interval 200 is more efficiently applied in indicating data to the receiver, as will become clear from the embodiments described below.
• the embodiments may allow for the capacity of the network to be utilized more efficiently as more users may be served within one symbol interval, more reliable data communication by means of diversity, or an increased data rate.
• the base station 400 capable of managing UWB based communication may cause indication of the distinct information unit to different users 402 to 416 in at least one pair of burst time intervals 202A to 202H, thereby increasing the maximum number of simultaneous users served.
• the time slots 202A to 202H are different time slots, the word "simultaneously" should be seen broadly to cover substantially simultaneous indication of data to the users 402 to 416. In this manner, the number of users served may be doubled from the prior art solutions.
• burst time slots 202A-202E, 202B-202F, 202C-202G, and 202D-202H need to be applied in the data indication to different receivers, although this is enabled by the embodiment.
• PPM i.e. BPM
• at least four of the eight burst time slots would have been empty.
• a pair need not be 202A and 202E, although so depicted for clarity in the Figures.
• the allocated time slots of one pair could be, for example, 202A and 202F.
• burst time intervals 202A to 202D are allocated to a first user and one of the burst time intervals 202E to 202H is allocated to a second user, which is different from the first user.
• These time slots may be modulated with another modulation method than the PPM. This may allow more reliability for the communication as no multi-user interference is present within a symbol half.
• the guard time may provide additional protection from interference.
• the time hopping may take place within the symbol half.
• the information on who transmits/receives and when to transmit/receive may be obtained from a spreading code broadcasted by a coordinator or polled from the coordinator, for example.
• the receiver (Rx) is allocated specific time slots when to listen to the channel as is well known in the UWB based communication.
• the Rx may further be informed that the specific receiver does not need to listen to the channel during a certain second burst time interval, normally reserved for indicating the opposite bit value when the PPM is utilized, if the second burst time interval is allocated to another receiver.
• the other receiver may then be informed that the specific second burst time interval is allocated to that specific receiver.
• the transmitted data carries an identifier of the receiver so that the receivers will know which data burst is targeted for it. It is also possible that a new spreading code is broadcasted or unicasted to the receivers so that the receivers obtain knowledge of the adjusted reception slots.
• the base station 500 capable of managing UWB based communication may cause indication of the distinct information unit to a same user in at least one pair of burst time intervals.
• one first burst time interval for example interval 202A and one second burst time interval, for example interval 202E
• both of these intervals 202A and 202E are used for indicating distinct information to the same user 502.
• the other burst time intervals could apply the burst position modulation (BPM).
• each pair of first and second burst time intervals may be adopted to indicate data to a specific user.
• the burst time intervals 202B and 202F which would in the BPM form a pair of intervals from which one would be empty, are both used in indicating distinct data to receiver 504, for example.
• the distinct information unit in at least one pair of burst time intervals represents different data, thereby improving data rate for the same user.
• the pulse position modulation, or burst position modula- tion it may occur that the first or second bit is used for channel coding purposes.
• the first or second bit may be a convolutional bit which does not carry any user data. This directly means that the receiver would get only one bit of user data per symbol interval 200.
• the pro- posed embodiment may allow the user 506 to receive at least two bits of information representing different data, a first bit in the burst time interval 202C and a second bit in the burst time interval 202G (or the one from the second burst time intervals 202E to 202H which is reserved for the same user 506, and would in the PPM represent the opposite bit value), for example.
• This way the data rate of a specific user may double from the prior art solutions.
• the distinct information unit in at least one pair of burst time intervals represents the same data, thereby improving diversity for the same user.
• the distinct information unit received by the UE 504 in burst time slots 202B and 202F, forming a pair may represent the same data.
• the transmitter 500 needs to communicate bit "1 " to the UE 504 with a high reliability.
• the transmitted will transmit a bit value "1 " in the slot 202B and a separate, distinct bit value "1 " in the slot 202F.
• the transmitted bursts, both representing the same data may then experience different propagation conditions including large and small scale fading. As a result, the UE 504 may more reliably receive the data as diversity is applied.
• only one of the burst time intervals 202A to 202D is allocated to a specific user and only one of the burst time intervals 202E to 202H is allocated to the same user.
• the other burst time intervals within the symbol duration may be empty. This may allow more reliability for the communication as no multi-user interference is present within a symbol half.
• the guard time may provide additional protection from interference.
• the time hopping may take place within the symbol half.
• diversity is obtained over a plurality of symbol time intervals by indicating the first distinct information unit in the first burst time interval within a first symbol time interval and the second distinct information unit in a second burst time interval within a second, different symbol time interval.
• This embodiment is shown in Figure 6.
• the Figure shows a plurality of symbol time intervals 601 , 603 and 605.
• only two burst time intervals 600A, 600B and 602A, 602B, and 604A and 604B are shown in each of the symbol time intervals 601 , 603 and 605, respectively. It may be seen that the burst time interval 600A and the burst time interval 602B are used for indicating information to the same user 502.
• the information in this embodiment represents the same data, thus reaching diversity over two consecutive symbol time intervals. Same is true for the user 504, when the first distinct information unit is indicated in the burst time interval 600B and another indication of a distinct information unit representing the same data is performed in the burst time slot 604A, that is, in a symbol time interval 605 which is distant from the symbol time interval 601 . This may ensure variety of propagation conditions for the indicated information units and thus increases reliability of the data transmission.
• the distinct information units in at least one pair of burst time intervals represents the same data for the same user and the distinct information units in at least one other pair of burst time intervals represents different data for different users and/or for the same user.
• Figure 5B where the burst time interval pairs 202A-202E, 202B- 202F, and 202C-202G are applied in transmitting information to specific users 502, 504 and 506, respectively.
• the indicated information may represent the same data or different data.
• the burst time slot 202D is applied in transmitting information to user 508 and the burst time slot 202H is applied in transmitting information to user 510, thus obtaining an increase in the number of users served.
• This hybrid embodiment allows flexibility in the data communication as the needs of different UEs may more efficiently be taken into account within one symbol time interval.
• the receiver such as the receiver 502 may obtain, within the symbol time interval, an indication of a distinct information unit in each of the first burst time interval and the second burst time interval.
• the receiver 508 may obtain, within the symbol time interval, an indication of a distinct information unit in only the first burst time interval or only in the second burst time interval.
• the second burst time interval may not be allocated to the receiver 508.
• the UE 508 obtains this allocation information from a broadcast, for example. As the UE 508 is not allocated in any of the second burst time intervals, the UE 508 may perform other functions/tasks dur- ing that interval.
• the receiver 508 when obtaining the indication in only one of the first burst time interval and the second burst time interval, may leave the other burst time interval from the transmitter 500 unlistened to. This may allow for better performance of the UE 508 as it need not use re- sources in listening to the channel during the second burst time interval. In the prior art solutions, the UE 508 would have listened to the channel in both of the first and the second burst time interval, even though the UE 508 would receive data in only one of them.
• the PPM may be applied for some users within the symbol time interval and only, for example, one pair of first and second burst time intervals may be applied according to one of the proposed embodiments.
• the number of pairs for which the solution of any of the presented embodiments is applied may be anything between one and the number of burst time intervals within one half of a symbol interval.
• the symbol time interval comprises a plurality of first and second burst time intervals, such as eight of both, and each first burst time interval and each second burst time interval is applied in indicating a distinct information unit.
• the PPM is not applied at all within the symbol time interval.
• At least one of the following may be applied as a modulation method for the indicated distinct information unit in each of the burst time intervals: on/off keying, pulse shape modulation, pulse amplitude modulation, pulse phase modulation, and differential phase shift keying.
• on/off keying pulse shape modulation
• pulse amplitude modulation pulse phase modulation
• differential phase shift keying differential phase shift keying
• another modulation method may be applied for the data transmitted during an on-state of the on/off keying, when the on/off keying is applied as the modulation method.
• the second modulation method may be a phase shift keying.
• the data rate within one symbol time interval may be increased as one burst time interval may carry two bits, one bit indicated by the on/off keying and another bit by the second applied modulation method.
• the second modulation method may be, for example, one of a pulse shape modulation, a pulse amplitude modulation, and a pulse phase modulation.
• a pair of burst time intervals for example, intervals 202A and 202E
• the user may obtain four information bits within one symbol interval, when the second modulation method is a binary modulation method, for example, which allows low complexity of the receiver.
• the parties of the data communication may employ a mechanism for indicating the applied modulation meth- od(s) to the receiver.
• Figure 7 depicts an example signaling exchange of the mechanism.
• the transmitter 700 i.e. the party who is to indicate information to the other party
• the transmitter 700 may decide that the pulse position modulation is not to be applied for the user data but instead the proposed solution of any of the embodiments is to take place.
• This decision may take into account the communication requirements, the capabilities of the transmitter 700, the capabilities of a receiver 750, for example.
• the transmitter 700 may decide to act accordingly.
• the Tx 700 may de- cide to apply an embodiment which allows an increased number of users to be served simultaneously, for example. Similar decision may take place when increased reliability or enhanced data rate is needed.
• the Tx 700 may de- termine at least one modulation method to be applied in the communication of user data between the transmitter and the receiver, wherein the determined at least one modulation method does not comprise the pulse position modulation. That is, the Tx 700 selects a modulation method other than the PPM+BPSK for the user data part of the communication. This may allow for increased flexibility in the communication system as the PPM+BPSKis not necessarily always applied.
• the Tx 700 obtains information from the Rx 750 regarding this determination of modulation method(s). For example, in an embodiment, the Tx 700 obtains information on which at least one modulation method is supported by the receiver 750 in step 703. Although not shown in Figure, the Tx 700 may obtain the information of supported modulation methods even before step 702. Then the knowledge of supported modulation meth- ods may be taken into account when determining whether to bypass the PPM+BPSK or not. This data may be communicated to the Tx 700 by applying known communication methods. As a result, the Tx 700 may determine the at least one modulation method from a group of supported modulation methods. The group may comprise at least one of the following non-limiting list: on/off keying, pulse shape modulation, pulse amplitude modulation, pulse phase modulation, and differential phase shift keying.
• the Tx 750 may also or instead provide measurement results to the Tx 750, wherein the measurement results indicate the channel propagation conditions between the Tx 700 and the Rx 750. Such a measurement may be conducted by means of known pilot signals, for example.
• the Tx 700 may perform the determination of at least one modulation method such that the selected modulation method corresponds to the prevailing channel conditions. For example, BPSK may be selected for a channel with poor conditions whereas a more demanding modulation method, such as QPSK, may be selected for a better channel.
• the transmitter 700 determines the at least one modulation independently without any assistance. This option may allow for a low overhead in the network and ease of implementation as the unit determining the modulation method may not need any information about the propagation characteristics of the channel, for example.
• the Tx 700 may select the modulation method based on requirements with respect to throughput, buffer size, etc., for example. For instance, when high data rate is desired, the applied modulation method may be on/off keying enhanced with a further modulation method during the on-state of the keying modulation. Thus, the Tx 700 may determine a further modulation method which is to be applied for the data transmitted during an on-state of the on/off keying, when the on/off keying is applied as the (first) modulation method.
• the QPSK may be applied to reach higher data rates.
• Coherent modulation methods such as the pulse phase modulation, which provide better performance, may be prioritized over non-coherent methods to allow for better throughput, for example.
• a person skilled in the art is familiar with criteria for selecting a suitable modulation method and thus the details are not discussed here.
• the at least one modulation method is deter- mined separately each time user data is to be indicated to the receiver 750. This option may allow selection of optimal modulation method for each data depending on the data amount, buffer size, for example.
• a medium access (MAC) layer of the Tx 700 determines the at least one modulation method.
• the MAC layer may receive a data packet form an upper layer and, before forwarding the data packet to a physical layer, the MAC layer determines the modulation method(s) and the transmission method for the data packet.
• the MAC may decide to bypass the PPM+BPSK and apply another modulation method. Such a decision may be based on predetermined rules. For example, it may be that the user data is agreed to be transmitted so that increased throughput is obtained. Alternatively, it may be decided that throughput for the one user is to be maximized or that reliability of the data transmission is to be increased by applying transmission diversity. Also, priorities between different data packet may play an important role.
• the transmission of data to the Rx 750 is performed at the physical layer (PHY) of the Tx 700. Therefore, the MAC layer may need to inform the determined at least one modulation method to the physical layer. There are several embodiments for this.
• the MAC of the Tx 700 and the PHY of the TX 700 perform a predetermined negotiation prior user data transmission.
• the MAC informs the PHY about the determined at least one modulation method by transmitting a message (PLMN-SET- MODULATION-METHOD. request, for example) comprising the information of the determined at least one modulation method before the user data is directed to the physical layer.
• the PHY may respond by confirming the set modulation method, for example. This embodiment may allow the communication to take place without modifying a header structure of a MAC frame, for example.
• the MAC layer may inform the physical layer about the determined at least one modulation method by adding an additional field to a header of the medium access frame structure, wherein the additional field carries information related to the determined at least one modulation method.
• the proposed embodiment adds a new field "Modulation method" to the MHR (MAC header) which precedes the MAC payload and the MAC footer (MFR) sections.
• the new field is used to indicate the selected modulation method(s) by applying certain amount of bits.
• a commonly known table may be used to indicate the modulation method with table indexes of certain amount of bits. For example, a bit combination "001 " may denote that BPSK is used in- stead of the PPM+BPSK (also known as BPM+BPSK).
• the MAC layer may inform the physical layer about the determined at least one modulation method by including information related to the determined modulation method in an existing at least one bit of the header (MHR) of the MAC layer frame structure. For example, a "Re- served" subfield of a "Frame control" field of the MHR may be applied in indicating the selected modulation method(s).
• MHR header
• a "Re- served" subfield of a "Frame control" field of the MHR may be applied in indicating the selected modulation method(s).
• This option has the advantage that the general structure of the "Frame control" field and thus the MHR remains the same. This is advantageous so that no significant re-configuration is needed for the Tx 700 or the Rx 750 of Figure 7.
• the "Reserved" subfield is always transmitted even though it carries no information to the physical layer of the Tx 700 or to the physical and MAC layers of Rx 750. Therefore, this embodiment takes those reserved bits efficiently into account.
• the purpose of the MHR (MAC header) of Figures 5B and 5C is to carry information to the MAC layer of the receiver 750.
• the MHR is read in the PHY layer of the Tx 700. This allows the PHY layer of the Tx 700 to advantageously know which modulation method(s) to apply.
• the standard 802.15.4a belongs to the family of the IEEE 802.15.4, which may also determine at least some specifications for the UWB communication to which the present embodiments may be applied.
• the TX 700 may add infor- mation related to the determined at least one modulation method in a header of a physical layer frame structure.
• an existing field is modified to carry information related to the determined at least one modulation method. Such modification may take advantageously into use any unused bits in any of the fields of the header.
• the field may carry, for example, three bits M2, M1 , and M0 which may be used to represent the selected at least one modulation method.
• the bits may be used to indicate the selected modulation method(s) for example by referring to a commonly (between Tx 700 and Rx 750) known table with indexes and modulation methods.
• the Tx 700 may apply modulation to the control and user data to be transmitted to the receiver 750. It is proposed to apply the pulse position modulation (also known as the burst position modulation, BPM) and BPSK in the transmission of the header of the physical layer frame structure to the receiver 750. In other words, the header is modulated according to the manner specified in the standard IEEE 802.15.4a. However, for the user data, a different solution may be used.
• the Tx 700 may apply the determined at least one modulation method, instead of the PPM+BPSK in the transmission of user data to the receiver. In other words, the user data is not modulated according to the standard IEEE 802.15.4a, i.e. not with PPM+BPSK. Instead, another different at least one modulation meth- od is advantageously applied, thus allowing for an increased reliability or throughput, for example.
• the data (including the header and the user data, at least) is indicated to the Rx 750.
• the PHY header is modulated in the predefined manner (i.e. by using the PPM+BPSK) and transmitted to the Rx 750 be- fore the user data is transmitted, the Rx 750 obtains knowledge of the to-be- used modulation method(s) for the user data.
• the acknowledgement procedures applied so that the Tx 700 obtains knowledge that the Rx 750 is now aware of the methods to be applied.
• the PHY data packet may be transmitted by applying the IR-UWB technique so that the synchronization preamble (SHR preamble) is transmitted first, followed by the header of the physical layer, and the actual user data is transmitted after the SHR preamble and the PHY header.
• the PHY layer packet is transmitted in short bursts and guard periods are placed for example between the PHY header and the user data. Because of this the Rx 750 has time to read the PHY header, extract the to-be-applied demodulation method, for example, from the added field in the PHY header, and (re)configure the receiver 750 to apply the determined at least one demodulation method before the actual user data needs to be demodulated.
• each of SHR preamble, PHY header and user data is modulated in a predetermined manner with the PPM+BPSK and there is no need to indicate any alternative modulation methods between the Tx 700 and the Rx 750.
• the Rx 750 may select a correct demodulation method and demodulate the data in step 712 of Figure 7. This is advantageous so that no user data is lost because of not applying the correct demodulation method right from the beginning.
• the Rx 750 may demodulate the header of the received PHY frame structure by using the predetermined PPM+BPSK.
• the Rx 750 may also determine, from the demodulated header, information related to the at least one modulation method applied in the communication of user data, wherein the at least one modulation method does not comprise the pulse position modulation, and then demodulate the received user data by using the determined at least one modulation method, instead of the pulse posi- tion modulation.
• the Rx 750 may examine the received bits and derive an applied modulation method based on the examination. Then the Rx 750 may change the predefined PPM modulation method into the one actually used. This option is simple from the transmitter point of view. However, this option may, with a high probability, lead to the fact that some of the bits in the beginning of the user data are lost.
• An embodiment, as shown in Figure 8, provides an apparatus 800 comprising at least one processor 802 and at least one memory 804 including a computer program code, wherein the at least one memory 804 and the com- puter program code are configured, with the at least one processor 802, to cause the apparatus 804 to carry out any one of the above-described processes.
• Figure 8 shows only the elements and functional entities required for understanding the apparatus 800. Other components have been omitted for reasons of simplicity. The implementation of the elements and functional entities may vary from that shown in Figure 8.
• the connections shown in Figure 8 are logical connections, and the actual physical connections may be different. The connections can be direct or indirect and there can merely be a functional relationship between components.
• the apparatus 800 may be comprised in a base station (also called a base transceiver station, a Node B, a radio network controller, or an evolved Node B, for example).
• the apparatus 800 may comprise a circuitry, e.g. a chip, a processor, a micro controller, or a combination of such circuitries in the base station and cause the base station to carry out the above-described functionalities.
• the apparatus 800 may comprise the terminal device of a cellular communication system, e.g. a computer (PC), a laptop, a tabloid computer, a cellular phone, a communicator, a smart phone, a palm computer, or any other communication apparatus.
• the apparatus is comprised in such a terminal device, e.g. the apparatus may comprise a circuitry, e.g. a chip, a processor, a micro controller, or a combination of such circuitries in the terminal device and cause the terminal device to carry out the above-described functionalities.
• the apparatus 800 may be or comprise a module (to be attached to the UE or to the base station) providing connectivity, such as a plug-in unit, an "USB dongle", or any other kind of unit.
• the unit may be installed either inside or attached to the apparatus with a connector or even wirelessly.
• the apparatus is capable of providing the indica- tion of the distinct information unit to the receiver according to any of the embodiments presented. In another embodiment, the apparatus is capable of obtaining the indication of the distinct information unit from the transmitter according to any of the embodiments presented.
• the apparatus 800 may comprise the at least one processor 802.
• the at least one processor 802 may be implemented with a separate digital signal processor provided with suitable software embedded on a computer readable medium or a memory, or with a separate logic circuit, such as an application specific integrated circuit (ASIC).
• the at least one processor 802 may comprise an interface, such as computer port, for providing communication capabilities.
• the apparatus 800 may be capable of transmitting data according to UWB protocol
• the apparatus 800 may comprise a pulse waveform generator 812, which may be responsible for producing desired waveforms to form a data burst, for example.
• a clock 810 may be re- sponsible of keeping the reference time synchronized between the transmitter and the receiver, for example.
• the waveform generator 812 may be omitted in the case the apparatus 800 is a receiver.
• the at least one processor 802 may comprise a UWB symbol circuitry 814.
• the circuitry 814 may be responsible of generating the UWB physi- cal layer symbol structure.
• the symbol structure may follow the IEEE 802.15.4a standard, for example.
• the circuitry 814 may thus concatenate the pulses obtained from the pulse waveform generator 812 to form a data burst that is transmitted to the receiver after being modulated with a specific modulation method in a modulation circuitry 816.
• the modulation circuitry 816 may select the applied modulation method(s) and perform the modulation separately for the PHY header and the user data, for example.
• the block 816 may be a demodulation circuitry capable of extracting the applicable demodulation method(s) and demodulating the received data according to the extract- ed modulation method(s).
• the modulation circuitry 816 is jointly shared by the layers.
• the at least one processor 802 may also comprise an allocation circuitry 818 for allocating the users with burst time intervals according to current needs.
• the circuitry 818 may also perform the allocation of data bursts or, in case of on/off keying being applied, lack of data transmission, in the burst time intervals according to any one of the embodiments.
• the block 818 may be responsible of knowing when to start listening to the channel as the block 818 may be aware of the allocation of the burst time intervals, etc.
• the apparatus 800 may further comprise radio interface components 806 providing the apparatus with radio communication capabilities with the radio access network.
• the radio interface components 806 may comprise standard well-known components such as amplifier, filter, frequency-converter, (de)modulator, and encoder/decoder circuitries and one or more antennas.
• the apparatus 800 may comprise a memory 804 connected to the processor 802.
• memory may also be integrated to the proces- sor 802 and, thus, no memory 804 may be required.
• the memory 804 may be for storing data related to the available/selected modulation methods, for buffering/storing data that is to be transmitted or is received, etc.
• the term 'circuitry' refers to all of the fol- lowing: (a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) combinations of circuits and software (and/or firmware), such as (as applicable): (i) a combination of processors) or (ii) portions of processor(s)/software including digital signal processors), software, and memory(ies) that work together to cause an apparatus to perform various functions, and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.
• This definition of 'circuitry' applies to all uses of this term in this application.
• the term 'circuitry' would also cover an implementa- tion of merely a processor (or multiple processors) or a portion of a processor and its (or their) accompanying software and/or firmware.
• the term 'circuitry' would also cover, for example and if applicable to the particular element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network de- vice, or another network device.
• the techniques and methods described herein may be implemented by various means. For example, these techniques may be implemented in hardware (one or more devices), firmware (one or more devices), software (one or more modules), or combinations thereof.
• the apparatus(es) of embodiments may be implemented within one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof.
• ASICs application-specific integrated circuits
• DSPs digital signal processors
• DSPDs digital signal processing devices
• PLDs programmable logic devices
• FPGAs field programmable gate arrays
• processors controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof.
• the implementation can be carried out through modules of at least one
• the software codes may be stored in a memory unit and executed by processors.
• the memory unit may be implemented within the proces- sor or externally to the processor. In the latter case, it can be communicatively coupled to the processor via various means, as is known in the art. Additional- ly, the components of the systems described herein may be rearranged and/or complemented by additional components in order to facilitate the achievements of the various aspects, etc., described with regard thereto, and they are not limited to the precise configurations set forth in the given figures, as will be appreciated by one skilled in the art.
• the apparatus comprises processing means configure to carry out embodiments of any of the Figures 1 to 8.
• the at least one processor 802, the memory 804, and the computer program code form an embodiment of processing means for carrying out the embodiments of the invention.
• the apparatus comprises means configured to perform the method of Figure 9.
• the method starts in step 900.
• the method ends in step 902 by applying ultra wideband, UWB, in communication of data between a transmitter and a receiver, wherein the UWB applies a physical lay- er symbol structure suitable for the application of a pulse position modulation.
• the method comprises causing, within a symbol time interval, an indication of a distinct information unit in each of a first burst time interval and a second burst time interval, wherein the first burst time interval is intended for representing a bit value to a certain user in the pulse position modulation, and a second burst time interval is intended for representing an opposite bit value to the same user in the pulse position modulation.
• the method ends in step 906.
• the pulse position modulation is also known as the burst position modulation.
• the apparatus comprises means configured to perform the method of Figure 10.
• the method starts in step 1000.
• the method ends in step 1002 by applying ultra wideband, UWB, in communication of data between a transmitter and a receiver, wherein the UWB applies a physical layer symbol structure suitable for the application of a pulse position modulation.
• the method comprises obtaining, within a symbol time interval, an indication of a distinct information unit in at least one of a first burst time interval and a second burst time interval, wherein the first burst time interval is intended for representing a bit value to a certain user in the pulse position modulation, and a second burst time interval is intended for representing an opposite bit value to the same user in the pulse position modulation.
• the pulse position modulation is also known as the burst position modulation.
• Embodiments as described may also be carried out in the form of a computer process defined by a computer program.
• the computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program.
• the computer program may be stored on a computer program distribution medium readable by a computer or a processor.
• the computer program medium may be, for example but not lim- ited to, a record medium, computer memory, read-only memory, electrical carrier signal, telecommunications signal, and software distribution package, for example.

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• 2011
  • 2011-09-30 FI FI20115956A patent/FI20115956A0/sv not_active Application Discontinuation
• 2012
  • 2012-09-26 WO PCT/FI2012/050924 patent/WO2013045760A1/en active Application Filing

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