JPH09284187A - Antenna changeover diversity transmitter and its system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the antenna changeover diversity transmitter and its system with less transmission error by switching sequentially multiple transmission antennas in response to a negative reply received via a reverse direction channel and sending again an information packet sent precedingly via a forward channel. SOLUTION: A transmission section 50 encodes and modulates an information packet from a data transmitter 60 and uses any of antennas T1-TM of a multiple transmission antenna 67 via a forward channel 68 being a communication medium to send the packet toward a reception section and awaits a reply from the reception section. When an affirmative reply comes from the reception section via a reverse channel 91, the transmission section 50 sends a succeeding information packet, and when a negative reply as a re-transmission request comes from the reception section, the transmission section 50 uses a switch 66 to select one of other antennas in place of a current antenna and sends the information packet having precedingly been sent by means of a repeat controller 92. Thus, transmission errors in a slow fading channel are reduced.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to the field of communications,
In particular, it relates to the field of wireless communication in slow fading channels.

[0002]

Antenna diversity is used to reduce the effects of multipath fading on channels that have slow fading characteristics. One form of antenna diversity is antenna switching diversity.

In a conventional antenna switching diversity transmission system, multiple antennas provide multiple channels (having an independent multipath fading characteristic), and are used when there is a change in channel conditions. In particular, the receiving unit constantly compares the received signal length with a predetermined threshold value that detects when the channel is in the over-damped state. If the received signal falls below that threshold, a clear message is sent on the reverse channel to convey information to the transmitter in poor channel conditions, causing the transmitter to have different antennas (eg, other channels). Switch to.

Since the conventional antenna switching diversity system uses a dynamic threshold value, it is necessary to add a processing circuit to the receiver for detecting and adjusting the threshold value. Also, for clear messages from the receiver, ARQ
The reverse channel used for the error protection protocol is set up instead.

Description of JPEG Embodiments The present invention is particularly suitable for transmitting JPEG images. Therefore, the present invention also uses the following embodiments of ARQ for unequal error protection. Weeruckody's patent application “Method and system for sending JPEG images”, application serial number (insert), March 31, 1995,
(See "Weerakoddy's JPEG Application").

JPEG is an international standard for still image compression. JPEG is named after a group that has advanced international standards (Joint Photographic Experts Group). The JPEG standard is "W.
B. Pembeiba, J.C. L. Michelle, JPEG Still Image Data Compression Standard (Van Nostrand Leanhold, New York, 1993).

Image data compressed JPEG includes two classes of segments. (I) an entropy coded segment displaying the image in 16x16 blocks,
(Ii) JP for interrupting and encoding header information, conversion, quantization table, and entropy encoded image data
A marker or a segment of a marker that contains other information required for the EG decoder. Among the markers is a restart marker that divides the entropy coded segment.

FIG. 12 shows the structure of a typical JPEG encoded image 50. At the start of image marker 10 and marker segment 10A, one or more image frames 20 (eg, a compressed image data stream) begin, and the end of image marker 30 ends one or more image frames. Marker segment 10
A defines a quantization table, an entropy coding (transformation) table and other parameters.

The frame header 22 and the marker segment 22A are generated at the start of each image frame 20. The frame header 22 begins at the start of the frame marker with the parameter values needed to decode the frame. For example, the frame header defines the basic attributes of the image (including image size, number of image components, compression mode, entropy coder used in the frame). Further, like the marker segment before the image frame, the marker segment 22A defines a quantization table, an entropy coding (conversion) table, and other parameters.

Each image frame 20 is composed of one or more scans 23 in the image data, one scan being one scan in the data for one or more components of the image. . The components of each scan are classified into one or more entropy coded segments 23B divided by restart markers 23C. Generally, the components of each entropy coded segment are further classified into one or more Minimum Coding Units (MCU), which are represented by blocks of 16x16 images.

The scan header 23A is used for the image frame 2
At 0, it is added to the start of each scan. The scan header 23A begins at the start of the scan marker followed by the values of the parameters required to decode the scan, such as the number of components in the scan and scan component specifications.

A marker segment begins with a "marker" which is a 2-byte hexadecimal code or word. The first byte is Oxff (Ox indicates that the byte in the image data stream is in hexadecimal format, and hex byte ff indicates a marker) in which the byte is always adjusted. The second byte is a "marker code" that identifies the function of the marker segment. The second byte is always a non-zero byte.

For example, the start of the image marker is Oxff
d8 and the end of the image marker is Oxffd9. In both cases in this case the byte ff indicates a marker and the marker codes d8 and d9 identify the marker as the start of the image and the end of the image marker respectively.

The tables in FIGS. 13 and 14 are JP
13 is a list of markers in the EG image, the table in FIG. 13 contains the start of the frame marker (which defines the entropy coding procedure used), the table in FIG. 14 shows all other or non-start frames. Contains markers. These markers fall into two categories: those without parameters and those with fixed parameters that are undefined and variable length sequences. 13 and 14, "V" in the length column of the table represents a variable length parameter in a known structure, and "N" in the length column represents , That the parameter sequence does not follow the marker, and that "U" is written in the length column indicates that the parameter sequence is not specified, and is indicated by a number in the length column. Represents the constant of the parameter byte following the marker. For example, in FIG.
The restart marker OxffdO has no parameter, and the parameter of the specified restart marker Oxffdd is included in the 4 bytes immediately following Oxffdd, and the start of the scan marker Oxffda is
Contains a variable length parameter sequence.

The first parameter in every marker segment is always a 2-byte code that represents the length of the parameter sequence. For example, the 2-byte code OxOO43 following the marker Oxffdb in the quantization table
Indicates that there are 67 parameter bytes following the marker (including the parameter having a length of 2 bytes).

Generally, markers having parameters that follow them are referred to as marker segments, although the term is used differently in this application.

As described in detail in Weeruckody's JPEG patent application, some JPEG images are more prone to transmission errors than others. In particular, markers or marker segments are more prone to error than entropy coded segments. The marker segment is defined as type I information and the entropy coded segment is defined as type II information.

Since the restart marker is said to be more error-prone than any other marker, the I-type information is
Further, it is separated into IA type and IB type information. The restart marker is defined as IB type information, and other markers are I
It is defined as type A information.

The transmission system of Weercoody's JPEG patent application takes into account the likelihood of errors of different types of JPEG information and uses "unequal error protection" during transmission. The most effective error protection applies to IA type information that is most prone to transmission errors. The same or lower level of protection applies to IB type information. Finally, the lowest level of error protection applies to the most error-prone type II information of the three types of information.

Error protection protocol power is a term known to those of ordinary skill in the art, usually measured with a minimum "free distance". The greater the free distance of the error protection protocol, the higher the effect of error protection. Error-prevention power is the signal-to-noise ratio (SNR)
It may be measured by the average bit error rate (BER) as well, but BER is relatively always overtime. The smaller the BER of the error protection protocol, the higher the effect of error protection.

When the unequal error protection is applied, the processing capacity of the transmission system is increased and the communication channel is used more efficiently in order to reduce the overhead and the bandwidth (for example, the number of redundant bits) requiring the error protection. can do.

The relative advantages of each type of information are described in JP
Considering the EG image, the effect is very large.
IA type information, which is the most important type of information, is generally JPE
It occupies less than 1% of the G image data stream.
The type information is generally 5 to 5 in the JPEG image data stream.
It accounts for only 10%. The remainder of the JPEG image data stream is occupied by type I information, which is the least error prone.

[0023]

Transmission errors often occur on the channel of wireless communications. One reason is multipath fading, due to scattering and reflection,
Multiplexed copies of information packets having different arrival times, amplitudes, and phases occur on the multipath and reach the receiving unit. The level of the received signal is reduced because the multiplexed copies of the information packets interfere with each other.

The level of the received signal has fallen below the level of the available threshold (signal-to-noise ratio (S
NR)), the channel is said to be over-damped. Due to a channel with slow fading characteristics, i.e. a channel that is very slow with respect to the data transmission rate, the overdamped state results in long burst bit errors.

What is needed is a cost effective antenna switch diversity transmission method and system for more efficiently using the reverse channel to transmit information over a slow fading channel.

[0026]

SUMMARY OF THE INVENTION The present invention provides a cost effective antenna switch diversity transmission method and system for more effectively using the reverse channel to transmit information over a slow fading channel. The present invention does not require dynamic threshold setting for determining the channel condition, and the receiver can be installed while suppressing the cost of the additional threshold setting circuit. Also, the present invention does not use the reverse channel to send explicit channel condition messages or explicit requests by the transmitter to change antennas if a channel is bad. Rather, the present invention requires the retransmission of erroneous packets, articulates the current channel conditions, and switches ARQ to switch antennas in poor channel conditions.
Use reverse channel with error protection protocol.

More specifically, the transmitter waits for an affirmative or negative acknowledgment from the receiver following transmission of each information packet on the forward communication channel. If no error is detected in the received packet, an acknowledgment (ACK) is sent to the transmitter via the reverse channel. On the other hand, if an error is detected, a negative acknowledgment (NAK) is sent by the receiver via the reverse channel to request the retransmission of the erroneous information packet, and the transmitter accordingly. Switches antennas and retransmits packets with errors.

[0028] One embodiment of the present invention is implemented in a transmitter. The transmission unit includes an error detection encoder that encodes an information packet to be transmitted with an error detection code. The transmitter also includes a modulator that modulates each encoded information packet. The first antenna transmits the coded and modulated information packet to the receiver via the first forward channel of the communication medium. The switch at the transmitter is configured to send a second response of the communication medium in response to a negative acknowledgment (NAK) from the receiver transmitted via the reverse channel of the communication medium.
The information packet is retransmitted from the second antenna via the forward channel.

The embodiment of the present invention also provides a transmitter according to the present invention for transmitting a JPEG image while preventing unequal errors.

[0030]

DETAILED DESCRIPTION OF THE INVENTION The present invention uses the ARQ protocol to prevent errors. Other protocols may be used, such as the hybrid ARQ protocol.

The ARQ protocol uses the reverse channel to require the receiver to retransmit an erroneous information packet, at which time it provides a relatively error-free wireless communication channel.

The transmitting unit in the ARQ-based transmitting system uses the error detection code to transmit the transmitted information packet in order to cause the receiving unit to detect whether there is even one information packet having an error to be retransmitted. Encode. The transmitter waits for a response from the receiver following the transmission of each encoded data packet on the previous communication channel, and if no error is detected in the received information packet, the information packet is received It is sent to the device, an acknowledgment is sent back to the transmitter, and conversely the next packet of information is sent to the receiver. On the other hand, when an error is detected in the received information packet, the receiving unit discards the information packet and sends a negative response to the transmitting unit, and the transmitting unit retransmits the information packet having the error.

The Hybrid ARQ protocol uses both an error detection code and an error correction code. In some hybrid ARQ protocols, an erroneous information packet is retransmitted only if the error correction code cannot correct the erroneous information packet. In other hybrid ARQ protocols, packets are encoded with an error correction code only when needed, e.g. in response to negative acknowledgments.

The present invention uses antenna switching diversity to mitigate the effects of multipath fading in slow fading channels and the number of ARQ retransmissions required. The antenna switch diversity of the present invention switches in response to negative acknowledgments of ARQ and hybrid ARQ protocols rather than explicit channel condition messages, switching antennas associated with dynamic thresholds.

For ease of understanding, the following embodiments of the present invention will be described functionally classified. The functions these categories describe are performed on shared or dedicated hardware,
The hardware includes, but is not limited to, those capable of executing software. In this embodiment, AT & T D
It consists of digital signal processor hardware such as SP16 and DSP32C and software that performs the operations described below. Very large scale integration (VLSI) of the present invention, similar to the hybrid DSP / VLSI embodiment.
Hardware embodiments may also be presented.

First Embodiment FIGS. 1 and 2 show a first embodiment of the present invention. A transmitter 50 is shown in FIG. 1, and a receiver 52 is shown in FIG.
Is shown.

The transmitting section 50 of FIG. 1 comprises a multiplex transmitting antenna (TA1-- comprising an error detecting encoder 62, a modulator 64, an antenna switch 66 and associated transmitting circuits (conventional carrier, pulse shaping and amplifying circuits). TAM)
67. Further, a repeat controller 92 is also provided.

The receiver 52 of FIG. 2 includes one or more receive antennas (RA) 69 containing associated receive circuitry (eg, consisting of low noise amplifiers, RF / IF bandpass filters, and matched filters). In addition, the receiving unit 52 uses the demodulator 7
1, an error detection decoder 73, and a repeat generator 90 are also included.

As shown in FIG. 1, the transmitter 50 receives the information packet from the data transmitter 60. The information packet is encoded by the error detection encoder 62 with a suitable error detection code known to one of ordinary skill in the art. The error detection code can cause the receiving unit to detect a transmission error in the information packet. A CRC-16 encoder that encodes an information packet with a 16-bit cyclic redundancy code is suitable for one error detection encoder.

Once the packet has been encoded with the error detection code, the packet is modulated by the modulator 64 and the antenna (T
A _{1 to} T A _M ). Any suitable modulator known to one of ordinary skill in the art may be used for modulator 64. A suitable modulator is a 4-DSPK modulator.

The receiving antenna 69 of the receiving section 52 is used to receive the information packet to be transmitted. Once received, the packet is demodulated by a suitable complementary demodulator 71. A 4-DPSK demodulator is suitable as a demodulator for the 4-DPSK modulator.

The error detection decoder 73 demodulates the modulated information packet and determines whether or not all packets have a transmission error. The decoder 73 usually reproduces the error detection code for each information packet and compares it with the error detection code transmitted in the information packet. Part 2
If the two codes match, it is estimated that the transmitted packet is error free. If the two codes do not match, then there is one or more errors in the transmitted packet. The error detection decoder 73 may be any suitable complementary error detection decoder.
For example, a CRC-16 decoder is suitable as a decoder for the CRC-16 encoder.

If no error is found in the information packet, the packet is forwarded to the data receiving device 75 and the repeat generator 90 sends an acknowledgment (ACK) to the transmitter 50 via the reverse channel. In response to the positive response, the repeat controller 92 of the transmission unit 50.
Sends the next data packet.

On the other hand, if an error is found in the information packet, the information packet is normally discarded and the repeat generator 90 sends a request to retransmit the packet via the reverse channel 91. The request for retransmission is called a negative acknowledgment (NAK).

Repeat controller 92 of transmitter 50
Responds to this request by retransmitting the erroneous information packet. Each transmitted packet is stored in a buffer or other suitable storage device prior to transmission for immediate use in retransmission credit.

The transmitter 50 also responds to negative acknowledgments (NAKs) by sequentially switching from the current transmit antenna to one of the other multiple transmit antennas 67 for transmitting information packets to the receiver. As mentioned above, a negative acknowledgment clearly indicates that the current transmission channel is poor. Switch 66 may be any suitable device known to one of ordinary skill in the art that functions to switch the antenna. For example, the switch 66 is an electronic switch or a magnetic switch.
Also, the switch 66 may be a hardware switch or a programmable software switch.

Second Embodiment A second embodiment of the present invention combines the antenna switching diversity system of the present invention with the embodiment of ARQ for unequal error protection described in the Weercoody JPEG patent application.

3 and 4 show a second embodiment of the present invention. In order to prevent unequal errors, this embodiment of the present invention shows that the ARQ protocol for type I JPEG information is smaller and more effective forward error correction (FE) for type II information.
C) Code is used.

A transmitting section 50A is shown in FIG. 3, and a receiving section 52A is shown in FIG. As an example, the transmission unit in FIG. 3 includes a separator 61, an error detection encoder 62, an error correction encoder 78, a block interleaver 79, 4-
DPSK modulator 80, multiplexer 65, switch 6
6. Multiple antennas (TA ₁ ~
TA _M ) 67 and a repeat controller 92.

As an example, the receiving section 52A in FIG.
A receive antenna (RA) 69 having associated receive circuitry,
Demultiplexer 70, 4-DPSK demodulators 71 and 8
1, block deinterleaver 82, error detection decoder 8
3, a combiner 74, and a repeat generator 90.

In all operations, the transmitter 50A in FIG. 3 receives the JPEG image from the data transmitter 60, separates the JPEG image into I-type and II-type information,
The type I and type II information is received from one of the antennas 67 via the first forward channel 68 of the communication medium through the receiver 52A of FIG.
Send to The transmitter 50A sends the type I and type II information in the multiplexed packet as shown in FIG. 11A, for example, via the first forward channel. In the receiver 52A of FIG. 4, the type I and type II information packets are processed, and if no error is detected, they are combined by the combiner
4 is recombined into a JPEG structure by, for example, JPEG
It is transferred to a data receiving device 75 such as a decoder. When an error is detected in the information packet, the repeat request is sent by the repeat generator 90 to the transmitting unit 50A via the reverse channel, and the error information packet is sent from the second antenna 67 to the second order of the communication medium. Transmit over directional channel 68.

In detail, the separator 61 in FIG.
Separates the JPEG image into type I and type II information. For example, the separator 61 uses a JPEG image for type I and II.
A digital signal processor (DSP) with appropriate software for separating into type information. As described above, the type I information is likely to cause a transmission error, and the type II information is the least likely to occur.

One frame, that is, one scan J
An example of how the DSP separates the type I information from the type II information in a PEG image is shown below. Other methods will be readily apparent to one of ordinary skill in the art for JPEG images having one or more frames 20 and one or more scans 23.

The DSP in this example is 1 indicating a marker.
Check the bytes of the JPEG image that are input for the hexadecimal byte ff. If an ff byte is detected, the DSP examines the next byte in the data stream, the marker code indicating the marker's function. The purpose here is to check whether the marker also contains a segment of the parameter following the marker in the data stream.

For example, as shown in the table of FIG.
If the next byte is a hexadecimal d8, the DSP recognizes that the marker is the start of an image marker with no parameters. In this case, the DSP separates the entire 2-byte marker (ffd8) from the JPEG stream.

However, the next byte is d in hexadecimal.
If b, the DSP recognizes that the marker is a defined quantization table marker (ffdb) with a variable length sequence of parameters that follows in the data stream. As mentioned above, the markers with the parameters that follow them are commonly referred to as marker segments.

In the case of marker segments, the DSP
Examine the next 2 bytes in the data stream after the 2-byte marker to determine the number of parameter bytes that follow the marker. The DSP then separates the 2-byte marker and its parameter byte from the JPEG data stream.

If the byte is not determined to be a marker or marker segment, it is considered to be Type II entropy coded information and is sorted from the JPEG data stream.

In addition to separating the I-type information from the II-type information, the DSP also adds location information in the I-type information so that the JPEG image structure can be recreated at the receiver. Various ways of doing this for one or more image frames 20 and one or more scans 23 will be readily apparent to one of ordinary skill in the art.

For example, as shown in FIG.
In one frame, that is, one scan JPEG image, all of the I-shaped markers and marker segments are I
This occurs before the Type I entropy encoded segment, with the Type I restart marker and the end of the image marker removed. Therefore, in a typical one frame, that is, one scan JPEG image, only the position of the end of the image marker and the restart marker need be sent to the receiver.

One way in which the DSP can encode the position of the end of image marker and the position of the start marker is to keep a running count of the number of bytes in the JPEG data stream to determine the number of bytes of the first restart marker (ffdO). It is used as the starting position for a modulo 8 sequence. For example, the restart marker (ffd
If O) is the 300th byte in the data stream, its byte number is 300.

Once the byte number of the first start marker has been determined, the DSP has a modulo-8 sequence (ff
It is possible to identify the relative byte positions of the remaining restart markers within d1-ffd7). In particular, DSP
Assigns a byte number to each next restart marker corresponding to the number of entropy coded bytes between it and the previous restart marker.

Regarding the end of the image marker, the DSP
Its position in the data stream is identified by its byte number. If there are 400 bytes in the JPEG image, the end position of the image marker is 400.

In an alternative embodiment, the restart marker position is transmitted to the receiver without the restart marker itself. This is because the restart marker is a known predetermined pattern (modulo 8 sequence: OxffdO, Oxffd1, Ox) generated by the receiver.
ffd2, Oxffd3, Oxffd4, Oxffd
5, Oxffd6, and Oxffd7).

Once the JPEG image has been separated into Type I and Type II information by separator 61, Type I and Type II information packets are distributed along individual Type I and Type II channels, as shown in FIG. Is encoded.

The I-type information packet starts on the I-type channel and is encoded by the error detection encoder 62. CRC-16 is used as the error detection encoder 62.
An encoder may be used.

In this embodiment, 4-DPSK modulator 64 modulates the encoded I-type information packet, but any suitable modulator known to one of ordinary skill in the art can be used. You may use the thing.

Moving on to the Type II encoding channel, the Type II information packet is passed by the encoder 83 using the FEC code to correct the error, for example, 1
/ 2 ratio, memory 4 convolutional code. The convolutional code is an ARQ that can cover type I information.
Less effective error correction than the error correction of the type II information.

The type II information packets encoded with the error correction code are interleaved by the block interleaver 83, giving some limited time diversity. The block interleaver 83 sets the bits of each encoded type II packet to m in the vertical direction.
Write to the × n memory matrix and then read in the horizontal direction. The interleaver randomizes burst errors that tend to occur on slow fading channels. Length n
If a burst error occurs, the interleaver effectively functions to convert the burst error into a single bit error.

In this embodiment, the modulated type I and I
The I-type information packet is multiplexed by the multiplexer 65. The purpose here is that after transmitting each type I packet, when the transmitter is waiting for an affirmative or negative response from the receiver, a time slot () that remains empty after transmitting each type I packet. 11 (A) t ₁ )
To use.

FIG. 11A shows the multiplexed I type and I type.
An example of an I-type information packet is shown.

In FIG. 11A, the multiplexer multiplexes L type II information packets between consecutive I type information packets. L can be fixed or variable. Further, for example, as shown in FIG. 11C, more than one I-type information packet is L
Can be transmitted after each group of type II information packets.

The multiplexed type I and type II information packets are sent to one of the antennas 67 (including the associated transmission circuits).
The receiver 52 via the first forward channel 68
Sent to A for processing.

As shown in FIG. 4, the multiplexed type I and type II information packets are received by the receiving antenna 69 of the receiving section 52A and demultiplexed along the individual decoding channels by the demultiplexer 70. It

The I-type information packet initially starts with the I-type demodulation channel and is complemented by the 4-DPSK demodulator 71.
And a complementary error detection decoder 7 demodulated by
3 is decoded. For example, if a CRC-16 error detection encoder is used to encode Type I information packets, a CRC-decoder is typically used to decode Type II packets.

As described with respect to the first embodiment, the function of the error detection decoder 73 is to reproduce the error detection code for each information packet and compare it with the error detection code transmitted in the I-type information packet. It is a thing. If the two codes match, it is assumed that there are no errors in the transmitted packet. If the two codes do not match, then it is assumed that the transmitted packet has at least one error.

If an error is found, the erroneous Type I information packet is discarded and a negative acknowledgment is sent by the repeat generator 90 via the reverse channel 91. In response, the repeat controller 92 and the switch 66 cause the transmitter 50A to transmit the erroneous information packet via the second forward channel. FIG.
The packet stream in (B) shows the same type I information packet (packet 1) being retransmitted.

If no error is found, the Type I information packet is sent to the combiner 74 and an acknowledgment is sent by the repeat generator 90 to the transmitter 50A via the reverse channel 91. As shown in FIG. 11A, the repeat controller 92 causes the transmitting unit 50 to respond in response to the positive response.
Let A send the next data packet.

Moving to the Type II decoding channel,
As shown in FIG. 4, the type II information packet is demodulated by the complementary demodulator 81.

Once demodulated, the Type II information packet is deinterleaved by the deinterleaver 82. The deinterleaver 82 performs the reverse operation of the interleaver 63. The bits of the incoming I-type information packet are stored horizontally in an m × n memory matrix and read vertically.

Then, the type II information packet is input to the error correction decoder 83. The Viterbi decoding algorithm is commonly used to decode the convolutional code by the error correction decoder 83. It will be apparent to one of ordinary skill in the art that other decoding algorithms suitable for decoding the type II information encoded with the error correction code may be used.

The combiner 74 combines the type I and type II information packets into a structure suitable for the data transmitter 75, which will normally have the original JPEG structure. The combiner 69 is suitably a digital signal processor (DSP) and is programmed to combine the type I and type II information.

For example, the DSP is programmed to place the end of the first start marker and the image marker at their respective byte number positions in the data stream. The other start markers are placed in byte positions, each relative to the position of the previous start marker. As described above, the relative position of each start marker was encoded by the separator 61 as the number of type II information bytes after the previous start marker. Finally, if only the position of the start marker is sent, the DSP may be programmed to generate a modulo 8 sequence of the start marker at the encoded relative byte positions as well. .

Third Embodiment In the third embodiment of the present invention, the I type information is further separated into the IA type information and the IB type information by applying to the transmission of the JPEG still image again, and the IA type information is more than the IB type information. Even with more effective error prevention.

5 and 6 show the third embodiment. A transmitter 50B is shown in FIG. 5, and a receiver 5 is shown in FIG.
2B is shown.

In this embodiment, the separator 61 is JP
Functioning to separate the EG image into Type I, Type IB, and Type II information, combiner 74 functions to combine all types of information into the appropriate JPEG structure for data receiving device 75.

The separator DSP of the second embodiment may be programmed to further separate the I-type information into IA-type and IB-type information. For example, the DSP separates or filters the start marker from other type I markers using the second byte of each marker that identifies its function. As shown in the table of FIG. 14, if the bytes after the ff byte are d0 to d7, the marker is a start marker and the DSP separates it from the JPEG data stream as IB type information. The location information is already the second
It may be encoded by a separator as described in the embodiment.

The combiner DSP may also combine all three types of information in the manner described in the second embodiment.

The third embodiment is a modification of the second embodiment shown in FIGS. 3 and 4. As shown in FIG. 3, the transmitter 50A (transmitter 50B in FIG. 5) has been modified to include an additional encoding channel for IB type information. 1A type information, like the I type information in FIG. 3,
Further processing along the same ARQ-based coded channel.

The IB type coded channel of the transmitter 50B in FIG. 5 comprises an error correction encoder 78A, a block interleaver 79A, and a 4-DPSK modulator 80A. These functional blocks correspond to the transmitting unit 50 in FIG.
The encoder 78, the block interleaver 79, and the modulator 80 connected to the A type II decoding channel of
Corresponding to Also, as an example only, the error correction encoder 78A is a so-called ratio 1/2, memory 4 convolutional code, and is an error correction encoder 78 for type II information.
Using a smaller and more efficient convolutional code similar to that used in.

By comparing FIG. 4 and FIG. 6, one is
The receiver 52A (receiver 52B in FIG. 6) of II is also II
Fig. 6 is a variant with individual coding channels for type information. The IA type information is decoded on the same ARQ based coding channel shown in FIG.

In particular, the IB type decoding channel of the receiving section 52B in FIG. 6 includes a demodulator 81A, a block interleaver 82A, and an error correction decoder 83A. The decoding process for IB type information is the same as the decoding process used for type II information because the same convolutional code is used for both IB type and II type information in this embodiment. As mentioned above, the Viterbi algorithm is based on the IB
It is commonly used to decode the convolutional code used in the type information.

Fourth Embodiment FIGS. 7 and 8 show a fourth embodiment of the present invention. 7 shows the transmitter 50C, and FIG. 8 shows the receiver 52C. These are modifications of the transmitter 50B and the receiver 52B in FIGS. 5 and 6, respectively.

This embodiment uses a hybrid ARQ protocol. As shown in FIGS. 7 and 8, the hybrid protocol is implemented by including the error correction encoder 63 in the transmission unit 50B of FIG. 5 and the complementary error correction decoder 72 in the reception unit 52B of FIG.
The purpose is to correct errors in erroneous packets before requesting retransmission of erroneous packets. In this regard, any suitable error correction code known to those of ordinary skill may be used.

Fifth Embodiment For the purposes of describing the fifth embodiment , in the fourth embodiment, the present invention multiplexes Type I and Type II information packets prior to modulation. Then, at the receiving end, the type I and type II information packets are demodulated before being demultiplexed.

This embodiment is shown in FIGS. 9 and 10. FIG. 9 shows the transmitting unit 50D, and FIG. 10 shows the receiving unit 52D.

The transmitter 50D is the transmitter 5 shown in FIG.
This is a modified example of 0A. As shown in FIG. 9, the multiplexer 65 of FIG. 3 is placed prior to all modulation,
Only modulator 64 is used to modulate the multiplexed Type I and Type II information packets.

A complementary receiver 52D is shown in FIG. The receiver 52D is a modification of the receiver 52A in FIG. As shown in FIG. 10, the receiving unit 52 of FIG.
A has been modified to place a demultiplexer 70 after demodulation of Type I and Type II information packets. Also, only demodulator 71 is left to demodulate the interleaved Type I and Type II information packets.

[0099]

The present invention is most effective in slow fading channels having a relatively small size and multiplexing rate. Further, the maximum effect can be obtained in the slow fading channel having a large number of transmitting antennas.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a transmission unit according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic configuration of a receiving unit according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing a schematic configuration of a transmission unit according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing a schematic configuration of a receiving unit according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a schematic configuration of a transmission unit according to a third embodiment of the present invention.

FIG. 6 is a block diagram showing a schematic configuration of a receiving unit according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a schematic configuration of a transmission unit according to a fourth embodiment of the present invention.

FIG. 8 is a block diagram showing a schematic configuration of a receiving unit according to a fourth embodiment of the present invention.

FIG. 9 is a block diagram showing a schematic configuration of a transmission unit according to a fifth embodiment of the present invention.

FIG. 10 is a block diagram showing a schematic configuration of a receiving unit according to a fifth embodiment of the present invention.

FIG. 11 shows a multiplexed Type I and Type II information packet of a JPEG image transmitted using the present invention.

FIG. 12 is a diagram showing a structure of a typical JPEG compressed image.

FIG. 13 is a table showing the start of each frame marker of a JPEG image.

FIG. 14 is a table showing non-start of each frame marker of a JPEG image.

[Explanation of symbols]

 50 transmitter 52 receiver 60 data transmitter 62 detection encoder 64 modulator 66 switch 68 forward channel 92 repeat controller 91 reverse channel

 ─────────────────────────────────────────────────── ———————————————————————————————————————————————— Inventor William Glensen United States, 20874 Maryland, Germantown, Crystal Rock Drive 19739, Number 11

Claims (23)

[Claims] 1. A transmitter (50) for transmitting an information packet to a receiver (52) via a wireless communication medium, wherein the transmitter (50) encodes the information packet with an error detection code. An encoder (78), a modulator (64) for modulating the encoded information packet encoded with the error detection code, and the reception of the modulated information packet via a first forward channel of a communication medium. A first antenna for transmitting to a unit (52) and a second antenna for transmitting the modulated information packet to the receiving unit (52) at the position of the first antenna via a second forward channel of a communication medium. And the receiving unit (52) transmitted from the first antenna to the second antenna via a reverse channel of a communication medium.
Switch that changes depending on the negative response from (66)
And a transmitting unit. 2. The transmitter of claim 1, wherein the first forward channel is a slow fading channel. 3. The transmitter of claim 1, wherein the second forward channel is a slow fading channel. 4. The error detection encoder (62) comprises a C
An RC-16 encoder, characterized in that
Sending part of. 5. Transmitter according to claim 1, characterized in that the modulator (64) is a 4-DPSK modulator. 6. The transmitter of claim 1, wherein the switch (66) is a hardware switch. 7. The transmitter of claim 1, wherein the switch (66) is a programmable switch. 8. The transmitter of claim 1, wherein the switch (66) is an electronic switch. 9. The transmitter of claim 1, wherein the switch (66) is a magnetic switch. 10. A method for transmitting an information packet to a receiving section (52) via a wireless communication medium, the transmission method comprising: encoding an information packet with an error detection code; and encoding the information packet with the error detection code. The information packet is modulated, the modulated information packet is transmitted from the first antenna to the receiving unit (52) via the first forward channel of the communication medium, and is transmitted via the reverse channel of the communication medium. Switching from the first antenna to a second antenna for transmitting the modulated packet via a second forward channel of a communication medium in response to a negative response from the receiving unit (52). How to send. 11. A transmitter (50) for transmitting a JPEG image via a wireless communication medium to a receiver (52) with unequal error prevention, wherein the transmitter (50) transmits the JPEG image as an I-type and II-type image. A separator (61) for separating into type information, an error detection encoder (62) for encoding the I type information with an error detection code, and an error correction encoder (78) for encoding the II type information with an error correction code. A modulator (64) for modulating the encoded type I and type II information, and transmitting the modulated type I and type II information to a position of a first antenna via a second forward channel of a communication medium. The first antenna for transmitting to the certain receiving unit (52), and the receiving unit (at the position of the first antenna via the second forward channel of the communication medium for the transmitted type I and type II information). 52) and a switch (66) for switching from the first antenna to the second antenna via the reverse channel of the communication medium in response to a negative response from the receiving unit (52). A transmission unit characterized by the above. 12. The first forward channel is a slow fading channel.
Sending part of. 13. The second forward channel is a slow fading channel.
Transmitter of 1. 14. The separator (61) is a digital signal processor.
Sending part of. 15. The digital signal processor comprises:
The transmitter of claim 11, which is an AT & T DSP32C. 16. The error correction encoder (78) comprises:
The transmission unit according to claim 11, wherein the type II information is encoded with a rate 1/2, memory 4 convolutional code. 17. A transmitter (50) for transmitting a JPEG image to a receiver (52) via a wireless communication medium with unequal error protection, wherein the transmitter (50) transmits the JPEG image to an IA type and IB type. A separator (61) for separating into type information, an error detection encoder (62) for encoding the IA type information with an error detection code, and an error correction encoder (78) for encoding the IB type information with an error correction code. A modulator (64) for modulating the encoded IA and IB type information, and a first (1) of a communication medium for the modulated IA and IB type information.
A first antenna for transmitting to the receiving unit (52) via a forward channel; and a second communication medium for transmitting the modulated IA type and IB type information.
A second antenna for transmitting to the receiving unit (52) at the position of the first antenna via a forward channel; and a second channel for transmitting from the first antenna to the second antenna via a reverse channel of a communication medium. The receiving unit (52)
And a switch (66) for switching in response to a negative response from the transmitting unit. 18. A transmitting section (50) for transmitting a JPEG image to a receiving section (52) via a wireless communication medium with unequal error prevention, wherein the transmitting section (50) transmits the JPEG image to a type I and type II image. A separator (61) for separating into type information, an error detection encoder (62) for encoding the I-type information with an error detection code, and a modulator (64) for modulating the encoded I-type information into II-type information. ), A first antenna for transmitting the modulated type I and type II information to the receiver (52) via a first forward channel of a communication medium, and the modulated type I and type II information. A second antenna for transmitting to the receiver (52) at the position of the first antenna via a second forward channel of the communication medium, and a reverse channel of the communication medium from the first antenna to the second antenna To The receiving unit (52) transmitted via
And a switch (66) for switching in response to a negative response from the transmitting unit. 19. A transmitting section (50) for transmitting a JPEG image to a receiving section (52) via a wireless communication medium with unequal error prevention, wherein the transmitting section (50) transmits the JPEG image to IA type and IB type. A separator (61) for separating into type information, an error detection encoder (62) for encoding the IA type information with an error detection code, and a modulator (64) for modulating the encoded IA type and IB type information. And transmitting the modulated IA-type and IB-type information to a first communication medium.
A first antenna for transmitting to the receiving unit (52) via a forward channel; and a second communication medium for transmitting the modulated IA type and IB type information.
A second antenna for transmitting to the receiving unit (52) at the position of the first antenna via a forward channel; and a second channel for transmitting from the first antenna to the second antenna via a reverse channel of a communication medium. The receiving unit (52)
And a switch (66) for switching in response to a negative response from the transmitting unit. 20. A method of transmitting a JPEG image to a receiving unit (52) via a wireless communication medium with unequal error prevention, the transmitting method separating the JPEG image into I-type and II-type information, The I type information is encoded with an error detection code, the II type information is encoded with an error correction code, the encoded I type information is modulated into II type information, and the modulated I type and II type information is encoded. The receiving unit (5) from the first antenna via the first forward channel of the communication medium.
2) and said modulated type I and II via a second forward channel of the communication medium in response to a negative response from said receiver (52) transmitted via the reverse channel of the communication medium. A transmission method comprising switching from the first antenna to a second antenna to transmit mold information. 21. A method of transmitting a JPEG image to a receiving unit (52) through a wireless communication medium with unequal error prevention, the transmitting method separating the JPEG image into IA type and IB type information, IA type information is encoded with an error detection code, the IA type information is encoded with an error correction code, the encoded IA type and IB type information is modulated, and the modulated IA type and IB type information is Communication is performed from one antenna to the receiving unit (52) via the first forward channel of the communication medium, and in response to a negative response from the receiving unit (52) transmitted via the reverse channel of the communication medium. Method and apparatus for manufacturing the modulated IA-type and IA-type fiber optic connector through a second forward channel of a medium to transmit IB-type information from the first antenna to a second antenna. A transmission method characterized by switching. 22. A method of transmitting a JPEG image to a receiving unit (52) via a wireless communication medium with unequal error prevention, the transmitting method separating the JPEG image into I-type and II-type information, Encoding type I information with an error detection code, modulating the encoded type I information into type II information, and transmitting the modulated type I and type II information from a first antenna to a first forward channel of a communication medium. Via the receiving unit (5
2) and said modulated type I and I via the second forward channel of the communication medium in response to a negative response from said receiver (52) transmitted via the reverse channel of the communication medium. A transmitting method, characterized in that the first antenna is switched to a second antenna to transmit the type information. 23. A method of transmitting a JPEG image to a receiving unit (52) via a wireless communication medium with unequal error prevention, the transmitting method separating the JPEG image into IA type and IB type information, Encoding IA type information with an error detection code, modulating the encoded IA type information and IB type information, and transmitting the modulated IA type and IB type information from a first antenna to a first forward channel of a communication medium. Via the second forward channel of the communication medium in response to the negative response from the receiving unit (52) transmitted to the receiving unit (52) via the reverse channel of the communication medium. A transmission method comprising switching from the first antenna to a second antenna to transmit the modulated IA-type and IB-type information.