Communication system and communication method

Abstract

To provide a communication system and the like that enable communication using a packet-based index modulation method that does not require frame synchronization.SOLUTION: In a communication system 1, a transmitter 3 and a receiver 5 communicate with each other using a packet-based index modulation method. The transmitter 3 transmits a c-1th packet and a cth packet to the receiver 5. The receiver 5 includes a differential PLIM transmission data reception processing unit 27, a reception control unit 29, and a receiving unit 25. In the receiver 5, when the receiving unit 25 receives the c-1th packet and the cth packet, the reception control unit 29 acquires frequency channel indexes ^kc-1 and ^kc, and reception time ^tc-1 and ^tc of the received respective c-1th packet and cth packet, and the differential PLIM transmission data reception processing unit 27 demodulates PLIM transmission data from the frequency channel indexes ^kc-1 and ^kc, and the reception time ^tc-1 and ^tc.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a communication system and a communication method, and more particularly to a communication system using a packet-type index modulation method. [Background technology]

[0002] Recently, the Internet of Things (IoT) has been attracting attention. The IoT consists of a network made up of a huge number of terminals, and includes both periodic and event-detection type communications. Furthermore, it is desirable for the IoT to be battery-powered and maintenance-free. For this reason, the application of LPWA (Low Power Wide Area), which enables low-power, wide-area communications, is expected.

[0003] LPWA is characterized by the Duty Cycle (DC). DC is the percentage of time that one transmitter can occupy a frequency channel for communication. For example, if DC = 1%, and the communication time is 1 second, then 99 seconds of standby time is required out of 100 seconds.

[0004] Due to DC, there are times when communication is absolutely impossible compared to the time used for communication. Even if a frequency channel is available, communication cannot be performed freely. Therefore, packet-level index modulation (PLIM) has been proposed as a modulation method that makes use of DC (see Non-Patent Document 1).

[0005] Figure 6 shows an example of a PLIM (see Non-Patent Document 1). Figure 6(a) is a diagram for explaining terminology. Time is divided into multiple time slots (TS). Packets are transmitted using a frequency channel and time slot designated by an index (IDX). The entire combination of frequency channels and time slots that can be used to transmit or receive one packet is called a frame F.

[0006] As shown in Figure 6(b), in PLIM, packets are transmitted using the frequency channel and time slot corresponding to the index representing the transmission bit. Specifically, for packet number c, the PLIM transmission bit (D c ) is used as the frequency index (k c ), and the lower bits are used as the time slot index (q c ) is assigned to the frequency index k of the packet with packet number c by the PLIM transmission bit of the packet with packet number c. c and time slot index q c is determined. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] K. Adachi, et al., “Packet-Level Index Modulation for LoRaWAN,” IEEE Access, 2021. Summary of the Invention [Problem to be solved by the invention]

[0008] The advantage of PLIM is that it can increase the transmission capacity by index modulation while satisfying DC, in addition to the transmission capacity of conventional packets.

[0009] However, the PLIM requires frame synchronization between the transmitter and receiver to detect the time slot index.

[0010] Generally, the transmitter terminal is expected to be inexpensive and have a low-precision oscillator, which causes clock drift, resulting in frame synchronization errors and time slot index detection errors.

[0011] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a communication system and the like that enables communication using a packet-type index modulation method that does not require frame synchronization. [Means for solving the problem]

[0012] A first aspect of the present invention is a communication system using a packet-based index modulation scheme, comprising a transmitter and a receiver, wherein the receiver comprises a differential PLIM transmission data reception processing unit, a reception control unit, and a reception unit, wherein the transmitter modulates PLIM transmission data and transmits a c-1th packet and a cth packet to the receiver, and when the reception unit of the receiver receives the c-1th and cth packets, the reception control unit modulates frequency channel indexes ^k of the received c-1th packet and the cth packet, respectively. c-1 and ^k c and reception time ^t c-1 and ^t c and the differential PLIM transmission data receiving processor obtains the frequency channel index ^k c-1 and ^k c and reception time ^t c-1 and ^t c The time slot index ^q calculated from c The PLIM transmission data is demodulated based on the c " is "k c " means the character with a "^" above it. The same applies to other descriptions of "^".

[0013] A second aspect of the present invention is the communication system of the first aspect, wherein the transmitter comprises a differential PLIM transmission data transmission processor, a transmission controller, and a transmitter, and in the transmitter, the differential PLIM transmission data transmission processor is configured to determine a frequency channel index k used when transmitting a c-1-th packet. c-1 and a part of the PLIM transmission data is used to determine the frequency channel index k of the c-th packet. c Determine the time slot index q used when transmitting the c-1th packet. c-1and the remaining PLIM transmission data, the time slot index q of the c-th packet c Determine.

[0014] A third aspect of the present invention is the communication system of the second aspect, wherein the differential PLIM transmission data transmission processor is configured to receive a frequency channel index k c-1 and the frequency channel index k of the cth packet using the addition of a portion of the PLIM transmission data. c Determine the time slot index q c-1 and the remaining PLIM transmission data are added to the time slot index q of the cth packet. c and the differential PLIM transmission data receiving processor determines the frequency channel index ^k c and ^k c-1 Difference and reception time ^t c and ^t c-1 The difference between the time slot index ^q c and demodulates the PLIM transmission data.

[0015] A fourth aspect of the present invention is a communication system according to any one of the first to third aspects, wherein the PLIM transmission data D of the c-th packet c is part of D α,c and the remaining D β,c The differential PLIM transmission data transmission processing unit is a combination of the PLIM transmission data D α,c and c-1st packet's frequency channel index k c-1 The frequency channel index k of the cth packet is obtained by modulating the number of frequency channels K with respect to the sum of c Determine the remaining PLIM transmission data, D β,c and c-1st packet's time slot index q c-1 The time slot index q of the cth packet is calculated by modulating the number of time slots Q of frame F with respect to the sum of c The differential PLIM transmission data receiving processor determines the frequency channel index ^k of the c-th received packet by equation (eq2).c Frequency channel index ^k of the c-1th received packet from c-1 If the subtracted value is not negative, a remainder operation is performed on the number of frequency channels K, and if it is negative, the number of frequency channels K is added and then a remainder operation on the number of frequency channels K is performed to obtain ^D α,c Determine the reception time of the cth packet ^t c The reception time of the c-1th packet from ^t c-1 The value obtained by subtracting slot The remainder of the result divided by Q is calculated as the time slot index ^q c By calculating the remaining PLIM transmission data of the c-th packet, ^D β,c can be determined directly from the time of receipt.

[0016]

number

[0017] A fifth aspect of the present invention is a communication system according to any one of the first to fourth aspects, wherein the differential PLIM transmission data transmission processing unit waits until the time frame of the immediately preceding packet has elapsed since the time at which the immediately preceding packet was transmitted before transmitting the cth packet, and then waits a time equivalent to the time slot index of the cth packet before transmitting the packet.

[0018] A sixth aspect of the present invention is a communication method in a communication system using a packet-based index modulation scheme, the communication system comprising a transmitter and a receiver, the receiver comprising a differential PLIM transmission data reception processing unit, a reception control unit, and a reception unit, the method comprising a transmitting step in which the transmitter modulates PLIM transmission data and transmits a c-1th packet and a cth packet to the receiver, and a receiving step in which the receiver receives the c-1th and cth packets, the receiving step comprising the reception control unit modulating frequency channel indexes ^k of the received c-1th packet and the cth packet, c-1 and ^k c and reception time ^t c-1 and ^t c and the differential PLIM transmission data receiving processor obtains the frequency channel index ^k c-1 and ^k c and reception time ^t c-1 and ^t c The PLIM transmission data is demodulated from the [Effects of the Invention]

[0019] According to each aspect of the present invention, the receiver operates differentially using information about the (c-1)th and cth packets to demodulate the PLIM transmission data of the cth frame from the frequency channel indexes and receive time slot indexes of the (c-1)th and cth packets, thereby achieving demodulation processing without the need for frame synchronization. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a block diagram showing an example of a configuration of a communication system according to an embodiment of the present invention; [Figure 2] 4 is a flowchart showing an example of the operation of the transmission processing unit 11 of the transmitter 3. FIG. [Figure 3] 10 is a flowchart showing an example of the operation of the reception control unit 29. FIG. [Figure 4]10 is a flowchart showing an example of the operation of the differential PLIM transmission data reception processor 27. FIG. [Figure 5] 5 is an example for specifically explaining the operations of FIGS. 2, 3, and 4. FIG. [Figure 6] FIG. 1 is a diagram illustrating an example of a conventional PLIM. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, examples of the present invention will be described with reference to the drawings, but the present invention is not limited to the following examples. [Example]

[0022] FIG. 1 is a block diagram showing an example of the configuration of a communication system according to an embodiment of the present invention.

[0023] The communication system 1 includes a transmitter 3 and a receiver 5 .

[0024] The transmitter 3 includes a transmission processing unit 11, a transmission information storage unit 13, and a transmission unit 15.

[0025] The transmission processing unit 11 is, for example, a processor, and operates under the control of a program. The transmission processing unit 11 includes a differential PLIM transmission data transmission processing unit 17 and a transmission control unit 19. The differential PLIM transmission data transmission processing unit 17 generates an index for a packet to be transmitted using the PLIM transmission data to be transmitted and the index of the immediately preceding packet. The transmission control unit 19 causes the transmitter 15 to transmit the packet using the generated index.

[0026] The transmission information storage unit 13 is a storage device such as a memory, and stores a database of information about packets to be transmitted.

[0027] The transmitter 15 is a communication device that realizes wireless communication, such as an antenna.

[0028] The receiver 5 includes a reception processing unit 21, a received information storage unit 23, and a receiving unit 25.

[0029] The reception processing unit 21 is, for example, a processor, and operates under the control of a program. The reception processing unit 21 includes a differential PLIM transmission data reception processing unit 27 and a reception control unit 29. The reception control unit 29 acquires information about packets received by the receiver 25. The differential PLIM transmission data reception processing unit 27 demodulates the PLIM transmission data of the received packet using the frequency channel index and time slot index of the immediately preceding packet.

[0030] The received information storage unit 23 is a storage device such as a memory, and stores a database of information about received packets.

[0031] The receiving unit 25 is a communication device that realizes wireless communication, such as an antenna.

[0032] In addition, in the transmitter 3, the transmission processing unit 11, the transmission information storage unit 13, and the transmission unit 15 operate in the same manner as the reception processing unit 21, the reception information storage unit 23, and the reception unit 25, respectively, and in the receiver 5, the reception processing unit 21, the reception information storage unit 23, and the reception unit 25 operate in the same manner as the transmission processing unit 11, the transmission information storage unit 13, and the transmission unit 15, respectively, thereby enabling transmission and reception.

[0033] 2 is a flow diagram showing an example of the operation of the transmission processing unit 11 of the transmitter 3. The transmitter 3 has a node number m.

[0034] The transmission processing unit 11 performs an initialization process (step STA1), for example, by setting a packet counter c to 0.

[0035] The transmission processing unit 11 generates the first packet (step STA2).

[0036] The differential PLIM transmission data transmission processor 17 sets an initial index, which includes a frequency channel index k0 and a time slot index q0.

[0037] The transmission control unit 19 transmits the first packet with the initial index (step STA3).

[0038] The transmission processing unit 11 stores the initial index (k0, q0) in the transmission information storage unit 13 in correspondence with the 0th packet, with the first packet being the 0th packet.

[0039] The transmission processing unit 11 increments c by 1 (step STA4).

[0040] The transmission processing unit 11 generates the c-th packet (step STA5), and the header of the packet contains information on the packet counter c and the node number m.

[0041] The differential PLIM transmission data transmission processor 17 determines the frequency channel index k that transmitted the (c-1)th packet. c-1 and time slot index q c-1 The information is acquired (step STA6).

[0042] The differential PLIM transmission data transmission processor 17 determines the frequency channel index k of the c-th packet based on the PLIM transmission data. c and time slot index q c is determined (step STA7).

[0043] The transmission control unit 19 transmits the c-th packet to the transmitter 15 using the frequency channel index k of the c-th frame. c and time slot index q c (step STA8).

[0044] The transmission processing unit 11 determines whether there is a next packet (step STA9). If there is a next packet, the process returns to step STA4. If there is no next packet, the process avoids transmitting a packet in the next frame (step STA10), waits for the frame time (step STA11), and determines whether there is a communication partner (receiver 5) in the network (step STA12). If there is not, the process ends, and if there is, the process returns to step STA9.

[0045] The processing of steps STA7 and STA8 will now be described in detail.

[0046] K is the number of frequency channels and Q is the number of time slots in frame F.

[0047] The index of the cth packet is the frequency channel index k c and the time index q c Includes:

[0048] Frame length is T frame,m Let the frame number of the c-th packet be T frame,m,c Let's say.

[0049] Transmission data of the cth packet (D-PLIM data) D c The upper bits of α,c , the lower bits are D β,c Let's say.

[0050] The initial indexes are, for example, k0=0 and q0=0, or are determined randomly.

[0051] The differential PLIM transmission data transmission processor 17 determines the differentiation index (D-IX) of the c-th packet according to the following formula (see step STA7).

[0052]

number

[0053] The transmission control unit 19 uses the determined differentiation index to transmit packets Qq from the (c-1)th packet transmission. c-1 +q c After waiting for time slots, frequency channel k c The c-th packet is transmitted using (see step STA8).

[0054] 3 and 4 are flow charts showing an example of the operation of the reception processing unit 21 of the receiver 5. In FIG.

[0055] FIG. 3 is a flow chart showing an example of the operation of the reception control unit 29.

[0056] The reception control unit 29 causes the reception unit 25 to wait on all K channels (step STB1). The reception control unit 29 determines whether a packet has been received (step STB2). The reception control unit 29 waits until a packet is received, and if a packet is received, the process proceeds to step STB3.

[0057] In step STB3, the reception control unit 29 demodulates the received packet.

[0058] The reception control unit 29 acquires information on the packet number c and the node number m from the header of the received packet (step STB4).

[0059] The reception control unit 29 calculates the frequency channel number ^k from the frequency at which the packet was received. c and receive time ^t c (step STB5). The reception control unit 29 obtains the node number m, the packet number c, and the frequency channel number ^k from the reception information storage unit 23. c and reception time ^t c Link and memorize them.

[0060] The reception control unit 29 determines whether or not there is a communication partner within the network (step STB6). If there is a communication partner, the process returns to step STB1. If there is no communication partner, the process ends.

[0061] FIG. 4 is a flow chart showing an example of the operation of the differential PLIM transmission data reception processor 27. As shown in FIG.

[0062] The differential PLIM transmission data reception processor 27 determines whether or not the reception controller 29 has performed processing when the packet was received (step STC1). The differential PLIM transmission data reception processor 27 waits until the packet reception processing is performed, and if the packet reception processing is performed, the process proceeds to step STC2.

[0063] In step STC2, the differential PLIM transmission data reception processor 27 determines whether the packet number c of the received packet is 0 and whether it is the first packet (step STC3). If it is the first packet, it demodulates the PLIM transmission data as the first packet, outputs it to the database, and returns to step STC1. If it is not the first packet, it proceeds to step STC4.

[0064] In step STC4, the differential PLIM transmission data reception processor 27 determines whether the (c-1)th packet of node number m has been received. If not, the process returns to step STC1. If the (c-1)th packet of node number m has been received, the process proceeds to step STC5.

[0065] In step STC5, the differential PLIM transmission data reception processor 27 receives the frequency channel index ^k of the (c-1)th packet of node number m. c-1 and reception time ^t c-1 Get the reception time ^t c and ^t c-1 to time slot index ^q c The PLIM transmission data is demodulated (step STC6) and stored in the received information storage unit 23 (step STC7). Then, the process returns to step STC1.

[0066] The processing of step STC6 will now be described in detail.

[0067] The packet number of the target packet is c (c>0), and the frequency channel index is ^kc , the reception time is ^t c Let the frequency channel index of the c-1th packet be ^k c-1 Let the reception time be ^t c-1 Let's say.

[0068] At this time, the received PLIM transmission data ^D c is estimated by the following formula, where ^D α,c is the high order bit, and ^D β,c is the lower bit, where (^k c -^k c-1 If T<0, add K before performing the modulus operation. slot is an arbitrary time slot length.

[0069]

number

[0070] If the previous packet has not been received due to packet loss, the system waits until the next (c+1)th packet is received, and demodulates the PLIM transmission data only when the consecutive packets are received.

[0071] Fig. 5 is an example for specifically explaining the operations of Fig. 2, Fig. 3, and Fig. 4. The number of frequency channels K is 4, and the number of time slots Q is 4. CH0 to CH3 are channels corresponding to frequency channel indexes 0 to 3, respectively.

[0072] FIG. 5(a) shows an example of modulation in the transmitter 3.

[0073] First packet P s0 The PLIM transmission data D0=0000 is transmitted with the initial indexes of frequency channel index k0=0 and time slot index q0=0.

[0074] Next packet P s1The PLIM transmission data D1 is 0101 (binary notation). The frequency channel index k1 is the s0 The frequency channel index k0=0 and the upper data D α,1 = 01 (binary notation, 1 in decimal notation) and perform a remainder operation with K = 4 to determine it as 1. The time slot index q1 is the time slot index of the previous packet P s0 The frequency channel index q0=0 and the lower data D β,1 =01 (binary notation, 1 in decimal) and perform a remainder operation with Q=4 to determine 1. P s1 uses frequency channel k1=1 to receive the previous packet P s0 It is transmitted after five time slots have elapsed since the previous packet P s0 The system waits for a time period of Q-q0=4 time slots from the transmission of the frame until the frame ends, and then waits for a time period of q1=1 time slot before transmitting.

[0075] Next packet P s2 The PLIM transmission data D2 is 1100 (binary notation). The frequency channel index k2 is the s1 The frequency channel index k1=1 and the upper data D α,2 = 11 (binary notation, 3 in decimal notation) and perform a remainder operation with K = 4 to determine it as 0. The time slot index q2 is the time s1 The time slot index q1=1 and the lower data D β,2 =00 (binary notation, 0 in decimal) and perform a remainder operation with Q=4 to determine 1. P s2 is the previous packet P s1 This means that the packet P s1 The packet waits for a time period of Q-q1=3 time slots from the transmission until the frame ends, and then waits for a time period of q2=1 time slot before transmitting.

[0076] Next packet P s3The PLIM transmission data D3 is 1011 (binary notation). The frequency channel index k3 is the s2 The frequency channel index k2=0 and the upper data D α,3 = 10 (binary notation, 2 in decimal notation) and perform a remainder operation with K = 4 to determine it as 2. The time slot index q3 is the time slot index of the previous packet P s2 The time slot index q2=1 and the lower data D β,3 = 11 (binary notation, 3 in decimal) and perform the remainder operation with Q = 4, determining it as 0. P s3 is the previous packet P s2 That is, the packet P s2 The system waits for a time period of Q-q2=3 time slots from the transmission of the frame to the end of the frame, and then transmits immediately since time slot q3=0.

[0077] FIG. 5(b) shows an example of demodulation in the receiver 5. Here, T slot = 1, but this is not the case.

[0078] First packet P r0 The counter number c is 0, and the signal is received at the initial frequency channel index ^k0=0 and time ^t0=0.

[0079] Next packet P r1 is received at counter number c=1, frequency channel index ^k1=1 (01 in binary notation), and time ^t1=5.

[0080] Top Data^D α,1 is calculated as follows: Subtracting the frequency channel index ^k0=0 of the previous packet from the frequency channel index ^k1=1 of the received packet gives 1. Since this is positive, a remainder operation is performed on this with K=4 to obtain the upper data ^D α,1 is determined to be 1 (01 in binary notation).

[0081] Lower Data^D β,1 is calculated as follows: Subtracting the reception time ^t0=0 of the previous packet from the reception time ^t1=5 of the received packet gives 5. This is called T slot After dividing by Q = 1, perform the remainder operation with Q = 4, and then perform the lower data ^D β,1 is determined to be 1 (01 in binary notation).

[0082] Next packet P r2 is received at counter number c=2, frequency channel index ^k2=0 (00 in binary notation), and time ^t2=9.

[0083] Top Data^D α,2 is calculated as follows: Subtracting the frequency channel index ^k1=1 of the previous packet from the frequency channel index ^k2=0 of the received packet gives -1. Since this is negative, add K=4 to this to get 3. A remainder operation with K=4 is performed on this to get the upper data ^D α,2 is determined to be 3 (11 in binary notation).

[0084] Lower Data^D β,2 is calculated as follows: Subtracting the reception time of the previous packet, ^t1=5, from the reception time of the packet, ^t2=9, gives 4. slot After dividing by Q = 1, perform the remainder operation with Q = 4, and then perform the lower data ^D β,2 is determined to be 0 (00 in binary notation).

[0085] Next packet P r3 is received at counter number c=3, frequency channel index ^k3=2 (10 in binary notation), and time ^t3=12.

[0086] Top Data^D α,3 is calculated as follows: Subtracting the frequency channel index ^k2=0 of the previous packet from the frequency channel index ^k3=2 of the received packet gives 2. Since this is positive, a remainder operation is performed on this with K=4 to obtain the upper data ^D α,3is determined to be 2 (10 in binary notation).

[0087] Lower Data^D β,3 is calculated as follows: Subtracting the reception time of the previous packet, ^t2=9, from the reception time of the packet, ^t3=12, gives 3. This is called T slot After dividing by Q = 1, perform the remainder operation with Q = 4, and then perform the lower data ^D β,3 is determined to be 3 (11 in binary notation).

[0088] In the differential transmission and reception of PLIM transmission data according to the present invention, packets are modulated and demodulated in relation to the immediately preceding packet, eliminating the need for frame synchronization and preventing erroneous detection of time slot indexes due to frame synchronization errors caused by clock drift between transmitters and receivers. [Explanation of symbols]

[0089] 1 communication system, 3 transmitter, 5 receiver, 11 transmission processing unit, 13 transmission information storage unit, 15 transmitter, 17 data transmission processing unit, 19 transmission control unit, 21 reception processing unit, 23 reception information storage unit, 25 receiver, 27 data reception processing unit, 29 reception control unit

Claims

1. A communication system using a packet-type index modulation method, Equipped with a transmitter and a receiver, The receiver includes a differential PLIM transmission data reception processing unit, a reception control unit, and a receiving unit, The transmitter modulates PLIM transmission data and transmits the (c-1)th packet and the cth packet to the receiver; In the receiver, when the receiving unit receives the (c-1)th and cth packets, The reception control unit receives the frequency channel indexes ^k of the received c-1th packet and the cth packet. c-1 and ^k c and reception time ^t c-1 and ^t c Get The differential PLIM transmission data reception processing unit is configured to receive a frequency channel index ^k c-1 and ^k c and reception time ^t c-1 and ^t c and demodulating the PLIM transmission data from the communication system.

2. The transmitter includes a differential PLIM transmission data transmission processing unit, a transmission control unit, and a transmission unit, In the transmitter, the differential PLIM transmission data transmission processing unit c--frequency channel index k used when transmitting the 1st packet c-1 and a part of the PLIM transmission data is used to determine the frequency channel index k of the c-th packet. c Determine c--the time slot index q used when transmitting the 1st packet c-1 and the rest of the PLIM transmission data, the time slot index q of the c-th packet c Determine The communication system according to claim 1 .

3. The differential PLIM transmission data transmission processing unit includes: Frequency channel index k c-1 and the frequency channel index k of the c-th packet by adding a part of the PLIM transmission data. c Determine Time index q c-1 and the remaining part of the PLIM transmission data to obtain the time slot index q of the c-th packet. c Determine The differential PLIM transmission data reception processing unit is configured to receive a frequency channel index ^k c and c-1 and the reception time ^t c and c-1 3. The communication system according to claim 2, wherein the PLIM transmission data is demodulated from the difference between the first and second signals.

4. PLIM transmission data D of the c-th packet c is a part of D α,c and the remaining D β,c It is a combination of The differential PLIM transmission data transmission processing unit is, by equation (eq1), Part of PLIM transmission data D α,c and the frequency channel index k of the c-1th packet c-1 The frequency channel index k of the c-th packet is obtained by performing a remainder operation on the addition of c Determine D, which is the remainder of the PLIM transmission data β,c and the time slot index q of the c-1th packet c-1 The time slot index q of the cth packet is obtained by performing a remainder operation on the addition of c Determine The differential PLIM transmission data reception processing unit is, by equation (eq2), The frequency channel index ^k of the c-th packet c Frequency channel index ^k of the c-1th packet from c-1 If the value obtained by subtracting K is not negative, a remainder operation is performed on the number of frequency channels K. If the value is negative, the number of frequency channels K is added and then a remainder operation on the number of frequency channels K is performed to obtain ^D α,c Determine The time ^t of the cth received packet c The reception time of the c-1th packet from ^t c-1 The value obtained by subtracting slot The remainder of the result divided by Q is calculated as the time slot index ^q c The remaining PLIM transmission data of the c-th packet is calculated by β,c 4. The communication system according to claim 2, wherein the communication system determines: [Equation 1]

5. 5. The communication system according to claim 1, wherein the transmitter waits until the time frame of the immediately preceding packet has elapsed since the time the immediately preceding packet was transmitted, and then waits a time equivalent to the time slot index of the cth packet before transmitting the cth packet.

6. A communication method in a communication system using a packet-type index modulation scheme, comprising: The communication system includes a transmitter and a receiver; The receiver includes a differential PLIM transmission data reception processing unit, a reception control unit, and a receiving unit, a transmitting step in which the transmitter modulates PLIM transmission data and transmits the (c-1)th packet and the cth packet to the receiver; a receiving step in which the receiving unit receives the (c-1)th and cth packets in the receiver; In the receiving step, The reception control unit receives the frequency channel indexes ^k of the received c-1th packet and the cth packet. c-1 and ^k c and reception time ^t c-1 and ^t c Get The differential PLIM transmission data reception processing unit is configured to receive a frequency channel index ^k c-1 and ^k c and reception time ^t c-1 and ^t c and demodulating PLIM transmission data from the

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