A method for signaling thestatus of a subcarrier in a mc network and a method for adaptively allocating the subcarriers in a mc network

The present invention relates to a method of transmitting a state of subcarriers used in a multicarrier (MC) system in which a plurality of subcarriers are used for parallel transmission of data packets. One of the MC mechanisms currently in use is applied to CDMA (Code Division Multiple Access) networks. In a CDMA network, each data symbol is spread over a bandwidth that is wider than the bandwidth required for transmission. As described above, the required spectral energy is lower than that of the non-diffusion spectral system, which can be used to allow parallel transmission channels in the same frequency band. Data transmitted on different channels can be distinguished by using different spreading codes for each channel. A data stream consists of a contiguous sequence of symbols or chips. Each symbol of a user's data stream is multiplexed by each element of the same spreading code and is therefore placed on multiple narrowband subcarriers.

Hereinafter, the term channel includes a code channel composed of a predetermined predetermined channel.

The present invention particularly relates to a wireless LAN (local area network) standard of the Institute of Electrical and Electronics Engineers (IEEE) that uses CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) as a medium access control (MAC) protocol. In CSMA, the node ensures that no other traffic is present before sending it over the shared physical medium. The physical medium can be the band of the electromagnetic spectrum of a wireless network such as a wireless LAN or the bus of an Ethernet (registered trademark) fiber optic or twisted pair cable. In a wireless network, multiple connections occur at the same time. Therefore, before attempting transmission, the transmitter makes an identification on the carrier to detect the presence of (encoded) signals from other stations.

The present invention also relates to a device capable of accessing a multi-carrier network operating in a predetermined bandwidth divided into a plurality of channels or subcarriers. The present invention also relates to a system that assigns a given channel or subcarrier to a previously existing transmission.

The present invention also relates to a method of appropriately assigning a channel or subcarrier of a multicarrier network that is not currently used or is considered to be optimal at present to a connection.

In a medium having multiple accesses, multiple nodes can transmit and receive concurrently. Concurrent transmission by multiple nodes results in frame collisions, in which case the receiver is unable to extract frames from duplicate received signals.

The device attempting to transmit may have a predetermined working bandwidth that is different from the working bandwidth of the intended receiver. The overlapping areas of these two bandwidths form a common bandwidth that can be used in current MC systems.

Two different multiple access mechanisms are CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) and CSMA / CD (Carrier Sense Multiple Access / Collision Detection). In the collision avoidance mechanism, the data station attempting to transmit first transmits a reservation signal, and secondly waits for all stations for a sufficient amount of time to receive the reservation signal before placing a frame. Transmission, and thirdly, if a station detects a reservation signal from another station during transmission, the station stops transmission for any time and then attempts transmission again. On the other hand, in the collision detection mechanism, a station that detects another signal during frame transmission stops transmission of the frame, transmits a collision representing the signal, and then arbitrarily before attempting transmission of the frame again. Wait for the time interval of.

In a wireless network, a large area can be covered when a subset of the network, such as clusters, are interconnected, for example, by forwarders or bridges. Subscribers in two clusters adjacent to each other cannot communicate directly when one subscriber is not within the reach of the other subscriber. The signal transmitted by the forwarder can be received by members of both clusters adjacent to each other. One of the mechanisms used to minimize the hidden node problem is the Ethernet on-demand mechanism "Transmission Request Signal / Transmission Permission Signal (RTS / CTS)". Before starting transmission of the data frame, the transmitting station transmits the RTS frame answered by the receiving station's CTS frame. The RTS and CTS frames have information about the transmission time length of the next data frame and the corresponding ACK frame (acknowledgement). By using the RTS / CTS mechanism, the third as a hidden node that cannot receive RTS frames because it is so far away from the transmitting station but can receive CTS frames because it is close enough to the receiving station. The station does not initiate its own transmission because it realizes the observed channel as non-idle.

A short duration frame interval (SIFS) of 16 μs can be placed between the two frames of the sequence RTS, CTS, DATA and ACK in the case of protocol 802.11a.

The MC-CDMA mechanism is a digital modulation technology that extends each data symbol of a data stream to the frequency domain as shown in FIG. 1 related to the prior art. Each of the original symbols or chips is placed on each of the narrowband subcarriers. The total channel bandwidth is divided into subcarriers, in this example four subcarriers f1 to f4. Symbol duration T_{b b}Assuming that, the spectral distance of the subcarriers is at least 1 / T_{b b}Must be.

In the example of FIG. 1, the original signal of 4 users is spread to 4 subcarriers, each of which is given one original signal (chip), thus given a spreading gain of 4. To make a distinction between the various chips of a channel or subcarrier, each chip is encoded when the spreading code used defines the chip. All data belonging to the same channel or subcarrier is extended by the same binary code sequence of length L.

For example, when using frequency shift keying, a 0 in the third position of the binary code sequence means that the coefficient π is added to the phase of the third chip imposed on the third subcarrier. However, the "1" at the third position in the binary code sequence corresponds to a phase shift of 0 with respect to the chip phase.

The symbol or signal finally transmitted by the nth subcarrier corresponds to the sum of each of the nth chips of the parallel k channel, and k = 4 in this example. The variable k corresponds to a valid user, subscriber, terminal or station, respectively.

Since different devices have different subsets of the available subcarriers in which the device can operate, the two devices attempting to initiate a connection have a common subcarrier or channel with which the device intends to exchange information. You need to find each set.

Each channel uses a variable center frequency in the bandwidth region. For example, a channel that requires a predetermined number (eg, 8) of subcarriers for operation is a subcarrier that is a common or overlapping subcarrier of the subcarriers available to the transmitter and the subcarriers available to the receiver. It is necessary to select a subcarrier from the group .

An object of the present invention is to provide a method of transmitting the state of subcarriers of a multicarrier network.

Another object of the present invention is to provide a method of appropriately assigning a predetermined subcarrier of a subcarrier of a currently idle multicarrier network to a connection.

Another object of the present invention is a multicarrier operating in a given bandwidth divided into multiple channels or subcarriers by a device capable of supporting the allocation of a given channel or subcarrier to a previously existing transmission. It is to provide a device that can access the network.

An object of the present invention is to provide a system that allocates a predetermined channel or subcarrier to a previously existing transmission.

In a method of transmitting a subcarrier state of a medium such as a multicarrier network operating in a predetermined bandwidth divided into a predetermined amount of channels or subcarriers with respect to a transmission method, when transmitting the state. The object is solved by a method characterized in that the terminal transmits a state signal representing the current state of each channel or subcarrier of the bandwidth. Within the network, the connection is set up, held, and then terminated. A portion of the channel of the medium can be used and therefore occupied while one connection is maintained. Once the connection is closed, these channels are idle again. The reason is that the state of the channel fluctuates over time and it is necessary to check the state of the channel before other connections are set up. The transmission of the channel state of the medium updates each node that identifies with respect to the current traffic.

The status signal can be transmitted on the medium as a dedicated packet, as part of or following a transmission packet, or as part of or following a data packet.

According to one variant, only dedicated packets are transmitted, in some cases with IFS. According to another variant, the state signal or information is transmitted as a field or information element in the transmitted packet and is therefore part of the transmitted packet. According to another variant, the state signal or information follows the transmitted packet without pause or wasted time, thus the state signal or information and the transmitted packet form a combined packet and the state signal is placed on the transmitted packet to be virtual. Is arranged. According to another variant, the state signal or information is transmitted as a field or information element in the header or other part of the packet. According to another variant, the state signal becomes part of the transmitted packet or follows the transmitted packet without pause or wasted time, so the state signal or information and transmitted packet form a combined packet and the state signal is transmitted. It is placed in a packet and virtually placed.

According to one example, the state signal is a binary sequence having an idle or "1" representing a valid channel or subcarrier and a "0" representing an occupied or invalid channel or subcarrier. The most significant bit of the binary sequence corresponds to the lowest frequency of the selected bandwidth.

According to a preferred example, the bit length of the binary sequence is equal to the total amount of channels or subcarriers of the medium as the states of all media are communicated in a single step.

The objectives are solved by the methods of independent claims 4, 8 and 10 as to how to properly allocate the channels or subcarriers of the network.

The proposed signal transmitted by the transmitting terminal represents which subcarriers are available from the perspective of the transmitting terminal, i.e., which subcarriers are available around or within a radius of the transmitting terminal. The transmitting terminal determines the state of each channel or subcarrier from the perspective of the transmitting terminal. Considering that receiving terminals with different positions and detection radii, and thus different perspectives, may predetermine the state of the channel or subcarrier and the receiving terminal identifies a different state than the transmitting terminal identifies. While transmitting a decision signal indicating which subcarrier to select. Ultimately, the transmitting terminal assigns a subcarrier to the previously existing data transmission based on the information in the decision signal. This method is particularly useful for networks such as Ethernet.

The proposed signal can be transmitted as a dedicated packet, as part of a transmission packet or following it, or as part of a data packet or following it.

According to one variant, only dedicated packets are transmitted, in some cases with IFS. According to another variant, the state signal or information is transmitted as a field or information element in the transmitted packet and is therefore part of the transmitted packet. According to another variant, the state signal or information follows the transmitted packet without pause or wasted time, thus the state signal or information and the transmitted packet form a combined packet and the state signal is placed on the transmitted packet to be virtual. Is arranged. According to another variant, the state signal or information is transmitted as a field or information element in the header or other part of the packet. According to another variant, the state signal becomes part of the transmitted packet or follows the transmitted packet without pause or wasted time, so the state signal or information and transmitted packet form a combined packet and the state signal is transmitted. It is placed in a packet and virtually placed.

The determination signal can be transmitted as a dedicated packet or as part of or subsequent transmission packet.

For the explanation of the two modifications, refer to the above explanation of the proposed signal.

According to one example, the proposed and decision signals are binary sequences having a "1" representing an idle or valid channel or subcarrier and a "0" representing an occupied or invalid channel or subcarrier. The most significant bit of the binary sequence corresponds to the lowest frequency of the selected bandwidth.

According to a preferred example, the bit length of the binary sequence is equal to the total amount of media channels or subcarriers as all media proposals and decisions can be communicated in a single step.

According to the method of independent claim 8, the transmitting terminal transmits a first management frame representing a fixed channel or subcarrier allocation, and the receiving terminal transmits a second management frame. Both of these frames are retrieved based on the channel or subcarrier allocation for previously existing data transmissions. During the connection time, the state of the medium can be changed because other connections can be terminated or started. Therefore, it is advantageous to change the subcarriers used or the subcarriers used need to be changed while the connection is maintained. The reason is that this method is called adaptive allocation because the subcarriers used are changed during the connection.

According to one example, the first and second management frames are binary sequences having an idle or "1" representing a valid channel or subcarrier and a "0" representing an occupied or invalid channel or subcarrier. The most significant bit of the binary sequence corresponds to the lowest frequency of the selected bandwidth.

According to a preferred example, the bit length of the binary sequence can communicate the first management frame in a single step and the second management frame in another single step according to the bandwidth of the entire medium, thus the channel of the medium. Or equal to the total amount of subcarriers.

According to the method of independent claim 10, the transmitting terminal is idle in terms of the transmitting terminal, that is, it transmits the first availability signal on a channel or subcarrier available around or within its radius of the transmitting terminal. To do. The receiving terminal then determines the state of the channel or subcarrier and transmits a second availability signal of the channel or subcarrier that is idle from the perspective of the receiving terminal, and the transmitting terminal is based on this information. Assign subcarriers to one or more previously existing data transmissions. This is a fast type of negotiation because the components of the first availability signal are transmitted in parallel with the components of the second availability signal.

According to a preferred example, the first and second availability signals are energy tone pulses. Since only the first and second availability signals are transmitted, it is preferable to select different frequencies for the first and second availability signals, and therefore a third recognized on the medium. Node can estimate whether it is the availability signal of the transmitting terminal or the availability signal of the receiving terminal.

In order to maximize the percentage of terminals in the transmission range of transmitting terminals that have information about the channel or subcarrier to be used, the transmitting terminal determines which channel or subcarrier was finally selected after the negotiation was completed. A similar notification signal can be transmitted.

In order to maximize the percentage of terminals that do not interfere with the planned transmission, the receiving terminal may transmit a similar notification signal indicating which channel or subcarrier was finally selected after receiving the notification signal. it can.

The purpose of the device is solved by the content described in any one of claims 17 to 23.

For the system, the objective is resolved as described in claim 24.

The methods, devices and systems according to the invention can be used in communication networks, wireless local area networks (WLAN) or wireless personal area networks (WPAN).

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. FIG. 2 shows a time chart of a transmitting terminal and a receiving terminal according to the first modification, in which case the proposed signal s1 indicating which subcarrier is available is either as part of the next transmitted packet (RTS) or. The decision signal s2, which is sent shortly thereafter and indicates which subcarrier can be selected taking into account the receiving terminal's information about the current traffic, is sent as part of the next transmit packet (CTS) or after the dormant SIFS. It will be sent immediately after that. The upper part of the time chart is related to the transmitting terminal or the transmitting source, and the lower part of the time chart is related to the receiving terminal or the receiver. The entire bandwidth, eg 20 MHz, is divided into multiple channels, eg 52 subcarriers. Twenty-four of these 52 subcarriers are shown. The lowest of the illustrated subcarriers is frequency f₀Have. The best of the illustrated subcarriers is frequency f₀+ nf_sIn this case, let n be the number of subcarriers, i.e. n = 24, and f_sIs the step frequency, for example, dividing the 20MHz bandwidth by the number of subcarriers n = 24, f_S= 0.83MHz. The signals s1 and s2 are transmission bit sequences of length k corresponding to the number of carriers k of the system. The description related to the frequency spectrum of the transmitting terminal is also valid for the receiving terminal.

FIG. 3 shows a time chart of a transmitting terminal and a receiving terminal according to the second modification. In this case, as a result of negotiation between the transmitting terminal and the receiving terminal, data executed on subcarriers that are not adjacent to each other are displayed. It is transmitted in parallel. After assigning a set of subcarriers to the planned data transmission, the transmitting terminal initiates transmission on the selected subcarrier and the receiving terminal transmits an approval signal on the channel or subcarrier group used by the transmitting terminal. ..

FIG. 4 shows a time chart of a transmitting terminal and a receiving terminal, in which case the selected subcarrier is changed after the RTS frame is transmitted. This means that the transmitting terminal transmits the transmission frame in the subcarrier selected by the transmitting terminal as appropriate when initiating the transmission. During SIFS, the receiving terminal examines the state of the subcarrier, and in this example, realizes the transmission frame of the third station, that is, the RTS frame following the proposed signal s3. In response, the receiving terminal responds with a transmission frame CTS following the decision signal s2 transmitted by a subcarrier different from the RTS frame. After SIFS, the transmitting terminal transmits data on the subcarrier that received the CTS frame. The reason is that the transmitting terminal has assigned these subcarriers as those to be used for data transmission. After further SIFS, the receiving terminal transmits the approval frame with the same subcarrier used for data transmission. Frames with signal s3 belong to alien connection and interference.

FIG. 5 shows a time chart of a transmitting terminal and a receiving terminal, in which case the connection is longer than the time required to transmit one data packet. In this case, the proposed set of subcarriers for the next fragment of the data packet is the signal s5 following the fragment ahead of the data packet, and the determined set of subcarriers for the next fragment of the data packet is in the ACK frame. It becomes the following signal s5.

FIG. 6 shows a time chart of a transmitting terminal and a receiving terminal according to another embodiment of the present invention, in which medium access is negotiated by a management frame. The management frame transmitted by the transmitting terminal includes the proposed channel allocation s6 answered by the receiving terminal by the management frame including the destination channel allocation s7. In this example, the first and second data packets are transmitted on the subcarriers negotiated in the management frame. In this example, another management frame s8 containing a binary sequence representing the current state of the subcarrier follows the second approval frame of the receiving terminal. The transmitting terminal allocates various subcarriers to the next (one or more) data packets based on this information.

FIG. 7 shows a time chart of a transmitting terminal and a receiving terminal according to another embodiment of the present invention, in which the media access and subcarrier set are negotiated by energy pulses. The transmitting terminal attempting to set up the connection reserves the currently compatible subcarrier by examining the subcarrier and transmitting the energy tone signal s9 of the associated subcarrier as the first availability signal AS1. The receiving terminal transmits a second availability signal AS2s10 with a subcarrier that can be selected for the data transmission to be performed. After hibernation, the transmitting terminal transmits the data packet with some or all of the subcarriers assigned for transmission according to the AS2s10 signal of the receiving terminal. The approval frame of the receiving terminal is transmitted on the same subcarrier.

FIG. 8 shows a time chart of a transmitting terminal and a receiving terminal according to another embodiment of the present invention, in which case the selected subcarrier is a subcarrier that was not in the proposed subcarrier group after transmitting the RTS frame. Is changed to. This means that the transmitting terminal transmits the transmission frame with the subcarrier selected as suitable at the start of transmission. The receiving terminal examines the state of the subcarriers from the viewpoint of the receiving terminal so that the subcarriers available on the transmitting side do not overlap with the previously proposed subcarriers. At the time of response, the receiving terminal responds by the transmission frame CTS following the destination signal s12 transmitted by the subcarrier different from the RTS frame. After SIFS, the transmitting terminal transmits data on the subcarrier that received the CTS frame. The reason is that the transmitting terminal has assigned these subcarriers as those to be used for data transmission. After further SIFS, the receiving terminal transmits the approval frame with the same subcarrier used for data transmission. This case is true when the terminal that has transmitted the proposal s11 for a group of subcarriers that can be used for data exchange does not necessarily predict a response on that subcarrier.

The present invention can be summarized as follows. The transmitting station needs to provide the receiving station with information about the proposed set of channels or subcarriers that it wants to occupy. On the other hand, the receiver needs to inform the transmitting station of the desired channel or subcarrier from the common channel or subcarrier group for which the receiving station predicts the optimum reception state. Transmission of a determined set of subcarriers can be performed on a packet-by-packet basis at the start of the connection, at predetermined intervals or on demand. Once the transmitter has identified a determined set of channels or subcarriers to be used, the transmitter may then be used for the receiver and all other terminals within the network. Send a set of accepted subcarriers. It opens the negotiations associated with the resources used so that other members of the network can identify and follow the negotiations. Therefore, other members identify which channel or subcarrier is reserved. Therefore, the transmitter does not necessarily have to perform the next step and does not have to transmit a selected set of subcarriers used for data transmission. Stations that recognize the RTS and / or CTS anticipate transmission on each of the carriers described as conforming and do not initiate transmission on such carriers. The station first finds the channel or subcarrier actually used by recognizing the data transmission.

One of the possible reasons why a final transmit handshake is required is that other terminals do not identify the frame, in which case a set of subcarriers or channels is proposed by the transmitter as well as the receiver. Determined by. This can be, for example, a case where a set of subcarriers or channels is transmitted in data frames or ACK frames. Another reason for the final handshake of the transmitter and receiver is that the receiver can propose one or more subcarriers that were not proposed by the transmitter. In this case, the devices around the transmitter do not have the opportunity to recognize the subcarrier or channel before initiating the data transmission.

In the present invention, it is proposed that the receiver select a subset of subcarriers or channels proposed by the transmitter. However, it is also possible for the receiver to select a subcarrier or channel that is completely different from the transmitter. This is possible. The reason is that it is the receiver that ultimately needs to be able to decrypt the data packet.

This transmitter assigns subcarriers or channel assignments to be transmitted on a data packet, on a transmit packet (such as RTS in IEEE 802.11), or after making a proposal and decision as a special packet for this purpose. I can tell you.

The third and second solutions are optimal solutions. The reason is that these additional messages are primarily directed to other terminals, which need to identify these messages. Therefore, it is necessary to use a broadcast message.

The receiver received by an authorization packet that can be placed on the receiver's own data transmission, on a transmit packet (such as RTS in IEEE 802.11), or as a special packet for this purpose. Approve subcarrier allocation. Again, the third and second solutions are optimal solutions.

Finally, the process of subcarrier or channel allocation can also be initiated by the receiver on which the transmission takes place. In this case, no negotiation is required. The receiver informs available subcarriers or channels at the beginning of the connection or from time to time. A terminal wishing to transmit data to this receiver selects a subset of possible subcarriers or channels for the receiver.

In the latter case, as described above, a final transmit handshake is preferred to inform the transmitter and terminals around the receiver of the selected set of subcarriers or channels.

<figref num="1">It is a figure which shows the prior art.</figref><figref num="2">The time chart of the transmitting terminal and the receiving terminal according to the first modification is shown.</figref><figref num="3">The time chart of the transmitting terminal and the receiving terminal according to the second modification is shown.</figref><figref num="4">Shows the time chart of the transmitting terminal and the receiving terminal in which the selected subcarrier is changed after transmitting the RTS frame.</figref><figref num="5">The time chart of the transmitting terminal and the receiving terminal which the connection takes longer than the time required to transmit one data packet is shown.</figref><figref num="6">A time chart of a transmitting terminal and a receiving terminal according to another embodiment of the present invention in which medium access is negotiated by a management frame is shown.</figref><figref num="7">Shown is a time chart of transmitting and receiving terminals according to another embodiment of the invention in which a set of medium access and subcarriers is negotiated by a management frame.</figref><figref num="8">The time chart of the transmitting terminal and the receiving terminal according to another embodiment of the present invention in which the selected subcarrier is changed after the transmission of the RTS frame and the newly proposed subcarrier does not belong to the proposed subcarrier group is shown. ..</figref>