This application claims priority to and the benefit of Korean Patent Application Nos. 10-2012-0100266 and 10-2013-0108501 filed in the Korean Intellectual Property Office on Sep. 11, 2012 and Sep. 10, 2013, the entire contents of which are incorporated herein by reference.
(a) Field of the Invention
The present invention relates to an apparatus and a method for transmitting a discovery signal. More particularly, the present invention relates to an apparatus and a method for discovering a plurality of neighboring devices without an infrastructure.
(b) Description of the Related Art
In a conventional art, a technology of wireless devices recognizing one another is representatively applied to Bluetooth. In Bluetooth, manufacturers and serial numbers of devices are coded so that the devices recognize one another using access codes as preambles. Such a method has drawbacks in that the MAC-ID that a host has may not be entirely expressed and devices must have a complicated Bluetooth only hardware characteristic (a frequency hopping diffusion spectrum modulation technique).
In order to demodulate such types of codes, a master/slave relationship must be established, and in order for a receiver to find codes, processes of analyzing and searching the codes are required. Since settings are based on the master/slave relationship, a network is also limitedly supported, there are limitations on a method of expressing the devices, and complexity of transmitting/receiving processes is large. In addition, since the method is suitable for ultra-short distance communications, the method is not suitable for long distance data communications.
Recently, Qualcomm announced a FlashlinQ standard for neighboring communications. The FlashlinQ standard also suggests a communication method of identifying neighboring devices. FlashlinQ is designed to identify the neighboring devices by medium access control (MAC) addresses and service IDs that are hardware (H/W) addresses of the devices without generating codes using special manufacturers and serial numbers, unlike in the Bluetooth. A physical distance range of data communications is about 1 km, which is large. The FlashlinQ requires a global synchronization reference signal so that transmission signals among devices do not overlap. Therefore, the FlashlinQ requires an infrastructure such as a mobile communication base station or a global positioning system (GPS). On the other hand, the Bluetooth does not require an infrastructure.
As described above, in the Bluetooth, neighboring devices may be synchronized with each other without the infrastructure. However, a plurality of neighboring devices may not be discovered due to a distance range or a standard. On the other hand, in the FlashlinQ, a plurality of neighboring devices may be discovered. However, dependency on the infrastructure required for synchronization among the devices is large.
An object of the present invention is to provide an apparatus and a method for transmitting a discovery signal to discover a plurality of neighboring devices without an infrastructure.
According to an exemplary embodiment of the present invention, a method for a device to transmit a discovery signal is provided. The discovery signal transmitting method includes generating a discovery signal including identification information of the device, and transmitting the discovery signal in an empty discovery slot among a plurality of discovery slots of a discovery interval. The discovery signal includes two orthogonal frequency division multiplexing (OFDM) symbols. One of the two orthogonal frequency division multiplexing (OFDM) symbols includes at least one tone. The identification information of the device is displayed by a position of a subcarrier corresponding to the at least one tone.
The other orthogonal frequency division multiplexing (OFDM) symbol of the two orthogonal frequency division multiplexing (OFDM) symbols may include a preamble.
The preamble may include a plurality of Golay sequences.
A length of the Golay sequences may be 128.
Transmitting the discovery signal in an empty discovery slot among a plurality of discovery slots of a discovery interval may include performing differential modulation on the at least one tone.
The discovery signal transmitting method may further include discovering a neighboring device from a discovery signal received in another discovery slot excluding the empty discovery slot among the plurality of discovery slots.
According to another exemplary embodiment of the present invention, a discovery signal transmitting apparatus for a device is provided. The discovery signal transmitting apparatus includes a signal generator and a signal transmitter. The signal generator generates a discovery signal including identification information of the device. The signal transmitter senses an empty discovery slot among a plurality of discovery slots of a discovery interval and transmits the discovery signal in the empty discovery slot. At this time, the discovery signal may include two orthogonal frequency division multiplexing (OFDM) symbols, one of the two orthogonal frequency division multiplexing (OFDM) symbols may include at least one Golay sequence used as a preamble, and the remaining one orthogonal frequency division multiplexing (OFDM) symbol may include the identification information of the device.
The signal generator may display the identification information of the device by positions of data subcarriers including a plurality of tones among a plurality of data subcarriers of the remaining one orthogonal frequency division multiplexing (OFDM) symbol.
Two tones may make a tone pair, and the signal transmitter may perform differential modulation on at least one tone pair.
Data subcarriers in which the plurality of tones are not included among the plurality of data subcarriers may be null subcarriers.
The discovery signal transmitting apparatus may further include a signal receiver. The signal receiver receives a discovery signal in at least one discovery slot among the plurality of discovery slots to discover a neighboring device.
In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification.
In the entire specification and claims, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements.
Hereinafter, an apparatus and a method for transmitting a discovery signal according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.
Referring to
In the discovery interval 10, each device finds neighboring devices.
Time synchronization among devices may be performed by a beacon signal transmitted and received in the synchronization interval 30.
Referring to
Referring to
A length of the Golay 128 sequences is 128, and the Golay sequences include “−1, −1, 1, 1, 1, 1, 1, 1, 1, −1, 1, −1, −1, 1, 1, −1, −1, −1, 1, 1, −1, −1, −1, −1, 1, −1, 1, −1, 1, −1, −1, 1, 1, 1, −1, −1, −1, −1, −1, −1, −1, 1, −1, 1, 1, −1, −1, 1, −1, −1, 1, 1, −1, −1, −1, −1, 1, −1, 1, −1, 1, −1, −1, 1, 1, 1, −1, −1, −1, −1, −1, −1, −1, 1, −1, 1, 1, −1, −1, 1, 1, 1, −1, −1, 1, 1, 1, 1, −1, 1, −1, 1, −1, 1, 1, −1, 1, 1, −1, −1, −1, −1, −1, −1, −1, 1, −1, 1, 1, −1, −1, 1, −1, −1, 1, 1, −1, −1, −1, −1, 1, −1, 1, −1, 1, −1, −1, 1”. The Golay sequences are used for estimating a channel. When the Golay sequences are used, a cross-correlator of the receiver may be simply realized. For example, it is possible to design a correlator of a structure in which addition operations are not performed 127 times but are performed seven times in order to obtain correlation of the Golay sequences having the length of 128.
The remaining one orthogonal frequency division multiplexing (OFDM) symbol of the two orthogonal frequency division multiplexing (OFDM) symbols includes data. The data may include identification information of a device. For convenience sake, the orthogonal frequency division multiplexing (OFDM) symbol including the data is referred to as an orthogonal frequency division multiplexing (OFDM) data symbol.
The OFDM data symbol displays information by a position of a tone. The information may be the identification information of the device. The OFDM data symbol includes a plurality of valid data subcarriers. The number of bits and information on the bits, that is, the identification information of the device, may be displayed by a position of a data subcarrier including the tone among the plurality of valid data subcarriers. The remaining data subcarriers excluding the data subcarrier including the tone among the plurality of valid data subcarriers are null subcarriers, and the tone has power by which the tone is distinguished from a null signal.
For example, in
As described above, information may be displayed by a position of one tone. However, information may be displayed by positions of at least two tones.
As illustrated in
To be specific, the 432 valid data subcarriers are divided into a plurality of domains, and the information is displayed by positions of data subcarriers including a plurality of tone pairs in the plurality of domains. The respective domains may represent positions of bits.
For example, it is assumed that the 432 valid data subcarriers are divided into 11 domains, that is, 64 data subcarriers, 32 data subcarriers, 16 data subcarriers, 64 data subcarriers, 16 data subcarriers, 32 data subcarriers, 16 data subcarriers, 64 data subcarriers, 32 data subcarriers, 32 data subcarriers, and 64 data subcarriers.
The 64 data subcarriers may represent 32 positions so that the 64 data subcarriers may display information of five bits. The 32 data subcarriers may represent 16 positions so that the 32 data subcarriers may display information of four bits. The 16 data subcarriers may represent eight positions so that the 16 data subcarriers may display information of three bits.
Therefore, the 64 data subcarriers, the 16 data subcarriers, the 8 data subcarriers, the 64 data subcarriers, the eight data subcarriers, the 16 data subcarriers, the eight data subcarriers, the 64 data subcarriers, the 16 data subcarriers, the 32 data subcarriers, and the 64 data subcarriers corresponding to the 11 domains may represent five bits, three bits, four bits, five bits, four bits, three bits, three bits, five bits, four bits, four bits, and five bits. As a result, information of a total of 43 bits may be displayed.
For example, “0000000000000000000000000000000000000000000” may be displayed by inserting 11 tone pairs into first subcarrier pairs of the 11 domains, respectively, as illustrated in
When the 432 valid data subcarriers are divided into the 11 domains, the 432 valid data subcarriers may be divided into the 64 data subcarriers, the 32 data subcarriers, the 16 data subcarriers, the 64 data subcarriers, the 32 data subcarriers, the 16 data subcarriers, the 64 data subcarriers, the 32 data subcarriers, the 16 data subcarriers, the 64 data subcarriers, and the 32 data subcarriers with a uniform pattern or periodicity. However, as described above, when the valid data subcarriers are divided into the domains with the uniform pattern or periodicity, a peak-to-average power ratio (PAPR) is increased when a signal of a frequency domain is converted into a signal of a time domain. Therefore, the 432 valid data subcarriers may be divided into, for example, the 64 data subcarriers, the 32 data subcarriers, the 16 data subcarriers, the 64 data subcarriers, the 16 data subcarriers, the 32 data subcarriers, the 16 data subcarriers, the 64 data subcarriers, the 32 data subcarriers, the 32 data subcarriers, and the 64 data subcarriers without the uniform pattern or periodicity so that the PAPR may be reduced.
As described above, since the identification information of the device of the total 43 bits may be displayed by one OFDM data symbol using the 11 tone pairs, the device may entirely express a medium access control (MAC) address, and a plurality of neighboring devices may be discovered from a plurality of discovery slots without the infrastructure in the frame structure of
Referring to
For example, in
In addition, when the differential modulation is performed, a receiver may improve receiving performance and may demodulate the two tones of the data subcarrier pair P4 with low complexity without a channel estimating process.
Referring to
The signal generator 810 generates a discovery signal including identification information of the device. The discovery signal includes two OFDM symbols as described above. One of the two OFDM symbols includes Golay sequences and the remaining OFDM symbol includes the identification information of the device. The identification information of the device may be displayed by a position of a data subcarrier including at least one tone in the OFDM symbol.
The signal transmitter 820 senses an empty discovery slot among a plurality of discovery slots and broadcasts a discovery signal in the empty discovery slot. At this time, the signal transmitter 820 may perform differential modulation on the data subcarrier including the at least one tone.
The signal receiver 830 listens to (receives) a discovery signal broadcasted by a neighboring device in at least one discovery slot among the plurality of discovery slots to discover the neighboring device.
According to the exemplary embodiment of the present invention, a plurality of neighboring devices may be efficiently discovered without an infrastructure.
The exemplary embodiment of the present invention is not realized only by the above-described apparatus and/or method, but may also be realized by a program for realizing a function corresponding to a configuration of the exemplary embodiment of the present invention and a recording medium in which the program is recorded. Such realization may be easily performed by those skilled in the art.
While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Number | Date | Country | Kind |
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10-2012-0100266 | Sep 2012 | KR | national |
10-2013-0108501 | Sep 2013 | KR | national |