The present invention relates to a method for identifying a terminal or user equipment (UE) in a wireless system.
This section introduces aspects that may be helpful in facilitating a better understanding of the invention. Accordingly, the statements of this section are to be read in this light and are not to be understood as admission about what is in the prior art.
In enhanced 4G wireless systems and especially in future 5G wireless systems, a large number of devices, e.g. user equipment devices (UE), will be present in the coverage area of a base station, e.g. an eNodeB. Many of these devices access the network only sporadically. These devices are machine-type devices (MTC), e.g. sensor devices. Sporadic traffic may also be caused by smartphone applications which only carry a few bits in the uplink, e.g. for triggering updates, calling weather forecasts or newsfeed updates.
In order to identify the user equipment devices, each device has its explicit address. When communicating with the base station, the explicit address has to be transmitted to the base station, causing overhead data. In case of a large number of user equipment devices, the explicit addresses need to provide a large address room, and hence the explicit addresses need to be long addresses. The longer the addresses are the more overhead data is produced. The overhead grows in relative size. When the amount of information data to be transmitted is comparatively small, the size of the actual explicit address data gets into the same order as the information data. This is the case e.g. in the mentioned MTC scenario.
The classical way of handling a large number of users in 4G wireless systems, e.g. LTE-A systems, is to use active state (RRC_CONNECTED) and idle state (RRC_IDLE). Devices which are not expected to have data to transmit for a longer time period are in idle state.
Devices which are idle or users which are active but not uplink-synchronized have to use the random access procedure before being able to transmit data. Furthermore, if there is no uplink resource allocated to a device for sending a scheduling request (SR), devices use the random access channel (RACH) to send a scheduling request (SR).
A random access procedure contains the following steps:
In a future scenario with sporadic traffic and a large number of machine-type devices, e.g. the so called internet of things, these devices will waste resources by causing a huge random access procedure overhead.
It is an object of the invention to enable efficient sporadic low-rate data transmission in such a scenario.
According to one embodiment, a method for detecting an implicit user ID of a received data packet is proposed. When a data packet is received, at least one transmission parameter of the data packet is determined. An implicit user ID of the data packet received is determined in dependence of the at least one transmission parameter.
A transmission parameter of the data packet received is to be understood as a parameter derivable from the data packet at the side of the receiver, e.g. the base station. Such a parameter is e.g. related to the coding of the data packet, a parameter of the RF signal used to transmit the data packet, etc. Examples of transmission parameters are discussed in the following.
An implicit user ID is to be understood as information related to the origin of the data packet, which is derivable from the data packet itself, e.g. from the physical characteristics of the received signal carrying the data packet, the direction of origin of the received signal, the encoding scheme of the data packet, etc. While an explicit address is composed of additional bits added to the user data of a data packet as an overhead in order to identify the origin of the data packet, the implicit user ID is derivable from the transmitted user data itself without adding additional bits.
Determining an implicit user ID of the data packet in dependence of the at least one determined transmission parameter has the advantage that transmission of explicit address data can be omitted, as the source of the data packet is determined by the implicit user ID. The information needed for determining the implicit user ID is available in the data packet anyway. Thus, no overhead data need to be sent to transmit such information and the overhead in the data transmission is reduced. Uplink synchronization is skipped for sporadic traffic. User equipment devices transmit their data right away in asynchronous manner. This is especially beneficial in future scenarios with a huge number of devices, each one generating only sporadic traffic on the network.
In one embodiment, a transmission parameter of the received data packet is its spreading code sequence, which was used for encoding the data packet. The spreading code sequence is determined and is used to determine the implicit user ID. The spreading code sequence is necessary to demodulate the received data packet anyway, thus using the spreading code sequence to determine the implicit user ID has the advantage that information which is available anyway is used.
In one embodiment, the spreading code sequence used for encoding the data packet, and thus the spreading code sequence determined by the method for detecting an implicit user ID is a tree structure spreading code sequence. An example for a tree structure spreading code sequence is e.g. a Walsh-Hadamard sequence. The spreading code sequence of a data packet which was encoded by a tree structure spreading code sequence is e.g. determined by a correlator-based tree-search of spreading subsequence sets. This reduces the processing complexity for determining the spreading code sequence significantly.
In one embodiment, a transmission parameter of the received data packet is at least one frequency on which the data packet has been received. In case of frequency multiplexing, the frequency on which a data packet was received is a discriminator to identify different origins of the data packet. In one embodiment, the data packet is received via a multi-carrier transmission system. Multi-carrier transmission systems are e.g. orthogonal frequency division multiplexing (OFDM) or filter-bank based multi-carrier (FBMC) transmission systems. In such a system, sub-band information or physical resource blocks (PRBs) are used to determine the at least one frequency on which the data packet is received. Alternatively, or in addition, a set of PRBs or a hopping pattern across a set of PRBs over time is used to determine the at least one frequency on which the data packet is received. This information is derived during processing of the received data packet and is used to define the address space of the implicit user IDs. FBMC systems have the advantage that side-lobes of the asynchronous signals of different devices are much weaker and thus have reduced inter-carrier interference (ICI) between neighboring carriers of different devices.
In one embodiment, the signal format is a combination of spreading and a multi-carrier transmission system, like multi-carrier CDMA (MC-CDMA), which is a combination of OFDM and CDMA. Instead of OFDM, other filter-bank-based multi-carrier techniques like FBMC may be used. In one embodiment, a single carrier system is used for transmission. Transmission systems using a single carrier are e.g. discrete fourier transform (DFT)-precoded OFDM transmission systems as a variant of single-carrier frequency-division multiple access (SC-FDMA) transmission systems.
In one embodiment, a multi-antenna receiver is used for receiving the data packet. The multi-antenna receiver indicates the spatial direction from which the data packet is received and allows estimation of the location of the user. This spatial signature is used to determine the implicit user ID. This offers one further degree of freedom for assigning implicit user IDs and expands the address room of implicit user IDs. In machine-type communication (MTC) systems, using spatial properties is attractive as many user equipment devices are sensor devices, which typically do not move. Their spatial characteristic is rather stable and provides reliable information for an implicit user ID.
In one embodiment, the power level of the signal of the received data packet is determined. In case the sender power is known, e.g. because it is the same for all user equipment devices, the received power level indicates the distance between the user equipment device and the receiver, as the attenuation of the signal is proportional to the distance between the user equipment device and the receiver. The determined power level is used to determine the implicit user ID. This offers one further degree of freedom for assigning implicit user IDs and expands the address room of implicit user IDs. In this way, the amount of implicit user IDs is significantly enhanced for applications that are employed over a large area.
In one embodiment, a look-up table is provided with stored characteristics of the user equipment devices which are registered. The look-up table includes one or multiple of the above mentioned characteristics, e.g. frequency, spreading code sequence, spatial characteristic and power level. The look-up table provides a fast way to determine the implicit user ID of a data packet received by comparing the determined characteristics of the data packet and the characteristics stored in the look-up table.
In one embodiment, the receiver assigns the implicit user ID characteristics to the user equipment devices e.g. using forward control signaling or higher layer control signaling.
In one embodiment, the data packet received contains an explicit address of the user. The explicit address is transmitted in an address field within the transmitted data. The user equipment device is identified by a mix of implicit and explicit address information. This has the advantage that the address space provided by the explicit address is enhanced by combining it with the implicit user ID and thus, the overall address space is enhanced. On the other hand, if the address space of the implicit user ID is not large enough to support all user equipment devices in the range of the receiver, the implicit address space is enhanced by additional explicit addresses transmitted in combination with the data. Especially in machine type communication scenarios with many user devices, this enhancement of the address space is desirable.
In one embodiment, an apparatus for receiving a data packet in a transmission system is proposed, wherein the apparatus performs a method according to the embodiments as described above.
In one embodiment, a transmission system for sending a data packet from a sender to a receiver is proposed. The transmission system comprises at least one apparatus for sending a data packet. The apparatus for sending the data packet applies a spreading code sequence for coding the data packet to be sent. Further, the transmission system comprises at least one apparatus for receiving a data packet as described in the embodiment above.
Some embodiments of apparatus and methods in accordance with embodiments of the present invention are now described, by way of examples only, and with reference to the accompanying drawings, in which:
The description and drawings merely illustrate the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof.
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In an exemplary embodiment with 100 PRBs and a spreading factor of 24, in case of one PRB transmission, 2400 implicit user IDs are available using spreading code sequence and frequency as distinguishing feature. A receiver equipped with four antennas with such a large set of users can easily find at least pairs of users being spatially orthogonal, thus increasing the implicit address space to 4800 devices. Using an eight bit explicit address in combination with the implicit user ID allows distinguishing more than a million user equipment devices 12 within the range of one receiver 10.
The functions of the various elements shown in the Figures, including any functional blocks, may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, the functions may be provided, without limitation, by digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read only memory (ROM) for storing software, random access memory (RAM), and non volatile storage. Other hardware, conventional and/or custom, may also be included.
Number | Date | Country | Kind |
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13305377.7 | Mar 2013 | EP | regional |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2014/055327 | 3/17/2014 | WO | 00 |