Patent Publication Number: US-7904779-B2

Title: Forward error correction and automatic repeat request joint operation for a data link layer

Description:
RELATED APPLICATIONS 
     This application is a U.S. National Stage Filing under 35 U.S.C. 371 from International Patent Application Serial No. PCT/RU2004/000535, filed Dec. 29, 2004, and published on Jul. 13, 2006 as WO 2006/073323 A1, which is incorporated herein by reference. 
     TECHNICAL FIELD 
     Embodiments of the invention relate generally to error correcting of communication signals. 
     BACKGROUND 
     A communication network typically includes equipment from various vendors sending data and information among the equipment in the network. To promote interoperability among vendor equipment, an open systems interconnection (OSI) reference model is a widely accepted structure to provide a standard architecture for such interoperability. Models similar to an OSI reference model may include a physical layer at the lowest structure layer followed by a data link layer. Above the data link layer, the model may include higher order layers such as a network layer, a transport layer, a session layer, a presentation layer, and an application layer. The layers may also include sub-layers. 
     The physical layer deals with the transmission of bit streams over a physical medium. It also deals with the mechanical, electrical, functional, and procedural characteristics to access the physical medium. The data link layer deals with the reliable transfer of information across the physical layer. It also sends blocks or frames for synchronization, error control, and flow control. The data link layer may include a medium access control (MAC) layer and a logical link control layer (LLC). Functions of the MAC layer, or sub-layer, may include assembling data into a frame with address and error-detection fields for transmission, dissembling frames and performing address identification and error detection on reception, and controlling access to the physical layer. The LLC layer may include functions such as interfacing to higher layers and performing flow and error control. 
     In addition to dealing with the interfacing of various vendor equipment, communication networks, for example computer networks, must deal with errors during data transmission in the communication channels of the network. A communication channel, whether it is a fiber optic channel, a co-axial channel, a wired channel, a wireless channel, or a bus connecting locations in a system over which large amounts of data are transferred, can add noise and error to information being transmitted over the channel. Various techniques may be used to deal with errors in data transmission. One approach is to use forward error correction (FEC) on a physical layer of the communication network. Another approach is to use automatic repeat requests (ARQ) on a data link layer of the communications network. 
     To correct for errors added by the communication channel, information can be sent in the form of codewords, where each codeword contains the same number of total bits and in which a number of the bits are information (message) bits and a number of bits are used for error correction. A codeword having a length of n bits includes k bits for the message length of the code and r=n−k redundant bits. The r bits are for error correction. To move to errorless data transmission, the error correcting capabilities of the code may be increased by using code redundancy. Alternatively, a large number of retransmission can be used. Either approach can add complexity to the communication process. However, there are cases of latency critical communications (real time audio and video), where the maximum data delay is limited, and the ARQ are either not allowed, or the maximum number of possible ARQ is strictly predefined. In high speed data communication what is needed is a reliable scheme that provides information with as few errors as possible, but at the same time can be implemented without a significant amount of complexity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a flow diagram of an embodiment of a method including forward error correction and automatic repeat requests performed above a physical layer of a communication network. 
         FIG. 2  shows a flow diagram of an embodiment of a method including encoding information in a data link layer with a high code rate. 
         FIG. 3  illustrates a block diagram of an embodiment of an apparatus to conduct forward error correction and automatic repeat requests above a physical layer. 
         FIG. 4  illustrates a block diagram of an embodiment of an apparatus to encode information in a data link layer with a high code rate. 
         FIG. 5  illustrates an embodiment of a structure of a communication system in which a FEC encoder and a FEC decoder operate above a physical layer. 
         FIG. 6  illustrates a block diagram of an embodiment of a communication network having a system with a forward error correction module with a high code rate in a data link layer to encode information and a system having a forward error correction modulation in a data link layer to decode data and a integrity control in the data link layer to generate automatic repeat requests. 
         FIG. 7  demonstrates an example of performance of an embodiment using a joint operation of forward error correction and automatic repeat request with respect to automatic repeat request only operation. 
         FIG. 8  illustrates a block diagram of an embodiment of a system having a forward error correction module to decode data and an integrity control to generate automatic repeat requests, where the decoding forward error correction module and the integrity control to generate automatic repeat requests are configured above the physical layer according to various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the invention. The various embodiments disclosed herein are not necessarily mutually exclusive, as some disclosed embodiments can be combined with one or more other disclosed embodiments to form new embodiments. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the embodiments of the present invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled. 
     A current procedure to provide errorless data transmissions uses retransmissions of the data. These data retransmissions are conducted independently of forward error correction techniques. Accompanying retransmissions is a delay in providing data. This generated data delay due to a large average number of required retransmissions may play a significant role in the quality of data transmission in a communications network. Use of a concatenated codes application to provide zero error probability may be useful if error blocks are matched with blocks of concatenated codes. However, the resulting concatenated codeword may become significantly large, which is not suitable for small sized data link layer packets. 
     Proposals for the physical layer in 10-gigabit (10G) Ethernet include coded modulation on the physical layer. Experiments show that the errors, after the physical level coded modulation, have a special distribution. Despite the fact that the overall bit error rate after coded demodulation on the physical layer is about 10×10 −8 , the errors are not uniformly distributed across the data frames. Using a more effective code on the physical layer leads to physical layer complication without any significant gain, because error correction will insert equal redundancy both in frames that have 1-2 errors and in frames that have 50 and more errors. In case of frames with 1-2 errors, the code redundancy may be superfluous. In case of frames with 50 and more errors, decoding may not correct all the errors and therefore may not provide an error probability equal to zero. A general solution for reliable communications uses FEC and ARQ separately, where retransmissions are used only to provide data integrity on layers above the physical level. To provide errorless data transmission, the error correcting capabilities of the code can be increased on the physical layer, providing code redundancy. Alternatively, a larger number of retransmissions on the data link layer may be used. 
     Coded modulation and error correction on the physical layer (PHY) for 10G Ethernet may include defined bit-error rate and error distribution after the physical layer error correction. Currently, a task force on 10G Ethernet for the IEEE 802.3™ standard has accepted use of coded modulation on the physical layer for 10G Ethernet PHY based on low-density parity check (LDPC) coded modulation schemes. LDPC codes provide a forward error correcting tool in high-speed communication systems due to the low decoding complexity and the bit-error rate (BER) achieved in an additive white Gaussian noise (AWGN) channel. Examples of known LDPC decoders include, among others, the min-sum algorithm, the a posteriori probability (APP) decoding algorithm, and the uniformly most powerful (UMP) decoder. 
     LDPC codes may use a parity check matrix containing mostly zeros and a limited number of ones. A binary (n, γ, ρ) LDPC code has a codeword length, or block length, of n bits and a parity check matrix with exactly γ ones in each column and exactly ρ ones in each row. In the LDPC code, each code bit is checked by γ parity checks and each parity check uses ρ code bits. Further, the code has a rate defined as R=k/n, where k is the number of message (information) bits in the codeword having n bits. 
     The operation of a data link network layer may depend on properties of the physical layer. Properties for the 10 G Ethernet physical layer to consider include the fact that the physical layer is not completely errorless. Further, the physical layer LDPC based coded modulation schemes use frames that have a block structure, due to the block nature of LDPC codes. For example, an overall frame size may be about 2000-6000 bits. Standard decoding of LDPC codes (belief propagation or any other fast decoding algorithms) may include decoding that is iterative, symbol-by-symbol decoding. With symbol-by-symbol decoding, the decisions about bits inside the whole LDPC codeword are made independently during decoding. However, in spite of the fact that LDPC codes are block codes, the error decoding of the whole codeword may not contain many error bits. For example, if the codeword length is 2000, possible situations include 1 error bit per codeword, 2 error bits, 50-100 error bits etc. Due to properties of LDPC codes, when LDPC codes are used for coded modulation on the physical layer of the 10G Ethernet network, the error distribution in data blocks after decoding and demodulation is non-uniform. There are three most probable cases: whole blocks are errorless, blocks contain 1-2 errors per each block, and blocks contain 50 and more errors per every block. To provide errorless data transmissions, errors may be corrected via ARQ on the data link layer. 
     Standards such as the IEEE 802.3™ standard have used the MAC sublayer to resolve collisions occurring under concurrent media access. 10G Ethernet is designed to be used only in full duplex transmission, but not in half-duplex. In full duplex mode there are no collisions, so a function of the MAC sublayer is to control data integrity via calculation and checking frame cyclic redundancy check (CRC) value, such as CRC32 value. If a frame checksum is not correct, the received frame is dropped and the MAC client reports that the error occurred, but no retransmission attempts are taken on the MAC level. Retransmission of a bad or dropped frame is initiated only two layers higher, on a transport layer such as TCP/IP, etc. Further, the Ethernet physical layer up to 1G is supposed to be errorless, but 10G Ethernet on its current stage does not meet such a requirement. Currently, traditional schemes on the data link layer do not consider the nature of the errors from the physical layer, and retransmissions are the only way to provide errorless transmission for the data link layer. 
     In an embodiment, signals received from a communication channel may be processed through joint operation above the physical layer of the communication network using forward error correction techniques and automatic repeat request techniques. Despite the fact that the overall bit error rate after coded demodulation on physical layer is about, for instance, 10×10 −8 , the errors are not uniformly distributed across the data frames as discussed above. Since providing code redundancy for frames having 1-2 errors is superfluous, and since decoding may not correct all the errors in case of frames with 50 and more errors, an embodiment for joint operation of FEC techniques and ARQ above the physical layer may provide reliable data communication. In an embodiment, to avoid superfluous retransmissions, a high rate FEC (rate about 0.98-0.999) in the data link layer is used that allows correcting errors in physical layer frames that have only 1-2 errors. The use of a specific code rate may provide defining characteristics for the code words generated. A request for retransmission may be conducted only for data in physical layer frames that contain a large number of errors, because correction of errors in these frames with FEC is inadequate and leads to unacceptable redundancy. Embodiments may be implemented in future 10G Ethernet data link layers and other communication networks with similar properties. 
     In an embodiment, correcting errors on the physical layer frames may be conducted separately. For embodiments applied to 10G Ethernet, due to the nature of 10G Ethernet physical layer errors, the FEC with very low redundancy above the physical layer is used to avoid retransmissions, but the retransmissions also are allowed, to provide overall errorless transmission. In contrast to concatenated codes, a joint FEC and ARQ approach is used to find a balance between redundancy and retransmissions. The usage of joint FEC and ARQ may lead to decreasing the number of retransmissions. 
       FIG. 1  shows a flow diagram of an embodiment of a method including forward error correction and automatic repeat requests performed above a physical layer of a communication network. At  110 , data is decoded using forward error correction techniques above the physical layer of a communication network if the number of errors in the data is equal to or less than an error threshold. In an embodiment, the error threshold is set at two errors or less. In an embodiment, the error threshold is the number of errors corrected using the forward error correction techniques above the physical layer for a given application. If the number of errors in the received data is less than or equal to the threshold and the errors are corrected, a message or indicator may be provided indicating that the decoding was a success. At  120 , if an error correcting module reports that there was a failure or if errors in data remain after decoding using forward error correction techniques, a request to retransmit the data using automatic repeat requests above the physical layer is performed. 
     In an embodiment, the FEC techniques may be performed in a data link layer. The ARQ techniques may be performed in a data link layer. In an embodiment, the FEC techniques and the ARQ techniques are both performed in the data link layer. In an embodiment, the FEC techniques may be performed in a medium access control layer. The ARQ techniques may be performed in a medium access control layer. In an embodiment, the FEC techniques and the ARQ techniques are both performed in the medium access control layer. The data decoded may be provided through a communication channel after the information in the data has been encoded in a data link layer using a forward error correction encoder with code rate of 0.98 or higher. In an embodiment, such a code rate may be about 0.99. In an embodiment, a code rate may be used that operates at a rate such that the number of retransmissions needed is two or less. In an embodiment, the data is received from a wireless communication channel. 
       FIG. 2  shows a flow diagram of an embodiment of a method including encoding information in a data link layer with a high code rate. At  210 , information is received. At  220 , the information is encoded in a data link layer to provide a codeword with a code rate of 0.98 or higher. At  230 , the codeword is transmitted. Encoding the information in a data link layer may be adapted to provide a codeword such that decoding the codeword includes decoding data representing the codeword using FEC techniques above a physical link layer, if the data has a number of errors equal to or less than an error threshold. If, after decoding using FEC techniques above a physical link layer, errors remain in the data, a retransmission request is generated above the physical layer using ARQ techniques. If, after decoding using FEC techniques above a physical link layer, an error correcting module reports a failure regarding the data, a retransmission request is generated above the physical layer using ARQ techniques. In an embodiment, the codeword is provided with a code rate of about 0.99. In an embodiment, the codeword is provided with a code rate such that the number of retransmissions needed is two or less. In an embodiment, the codeword may be transmitted in a wirelessly communication channel. 
       FIG. 3  illustrates an embodiment of an apparatus  300  to conduct forward error correction and automatic repeat requests above a physical layer. Apparatus  300  may include an integrity control  310 , a forward error correction module  320 , and a receiver  330  configured in a physical layer  340  to communicate in a network. Integrity control  310  and FEC module  320  are configured above physical layer  340 . FEC module  320  may be configured to decode information from data acquired by receiver  330 , if the data has a number of errors equal to or less than an error threshold. If FEC module  320  corrects the errors, FEC module may be in a “success” state and may provide an indication of such a state. In an embodiment, the error threshold is two errors or less. In an embodiment, the error threshold is the number of errors corrected using FEC module  320  above the physical layer for a given application. If errors remain in the code after decoding using FEC module  320  or if FEC module  320  reports a failure regarding the data, integrity control  310  uses ARQ techniques to request retransmissions of the data. The error threshold is not limited to two errors or less but may be set to appropriate values for the application in which the embodiment is adapted. 
     In an embodiment, FEC module  320  may be adapted to operate in a data link layer. Integrity control  310  configured to apply ARQ techniques may be adapted to operate in a data link layer. In an embodiment, FEC module  320  and integrity control  310  configured to apply ARQ techniques may both be adapted to operate in a data link layer. In an embodiment, FEC module  320  may be adapted to operate in a medium access control layer. Integrity control  310  configured to apply ARQ techniques may be adapted to operate in a medium access control layer. In an embodiment, FEC module  320  and integrity control  310  configured to apply ARQ techniques may both be adapted to operate in a medium access control layer. In an embodiment, FEC module  320  may operate to decode data having information encoded in a data link layer using a forward error correction encoder with code rate of 0.98 or higher. In an embodiment, apparatus  300  may be configured as a wireless device. 
       FIG. 4  illustrates an embodiment of an apparatus  400  to encode information in a data link layer with a high code rate. Apparatus  400  may include a forward error correction module  420  configured in a data link layer  425  and a transmitter  430  configured in a physical layer  440  to communicate in a network. FEC module  420  is adapted to encode information to provide a codeword with a code rate of 0.98 or higher. In an embodiment, the code rate is about 0.99. Transmitter  430  sends the encoded codeword onto a communication channel. 
     In an embodiment, forward error correction module  420  is configured to provide the codeword such that the codeword is adapted to undergo forward error correction techniques above a physical layer to decode data representing the codeword if the data has a number of errors equal to or less than an error threshold. In an embodiment, the error threshold is two errors. If, after decoding using FEC techniques above a physical link layer, errors remain in the data, a retransmission request is generated above the physical layer using ARQ techniques. If, after decoding using FEC techniques above a physical link layer, an error correcting module reports a failure regarding the data, a retransmission request is generated above the physical layer using ARQ techniques. In an embodiment, the codeword is provided with a code rate of about 0.99. In an embodiment, the codeword is provided with a code rate such that the number of retransmissions needed is two or less. In an embodiment, apparatus  400  is configured as a stationary wireless device. 
       FIG. 5  illustrates an embodiment of a structure of a communication system  500  in which a FEC encoder  524  and a FEC decoder  526  operate above a physical layer. Communication system  500  may include network node  504  having FEC encoder  524  and network node  506  having FEC decoder  526 . Network node  504  may include a host system  514  communicatively coupled to a transmitter  534 . Host system  514  may be communicatively coupled to transmitter  534  over a bus that is compatible with Peripheral Component Interconnect (PCI) or with PCI express. Transmitter  534  transmits codewords encoded from information provided to encoder  524 . FEC encoder  524  may be configured as part of transmitter  534  or external to transmitter  534  and may receive the information from host system  514 . In an embodiment, FEC encoder  524  operates above a physical layer in a manner similar to one or more embodiments described herein. 
     Network node  506  may include a host system  516  communicatively coupled to a receiver  536 . Host system  516  may be communicatively coupled to receiver  536  over a bus that is compatible with PCI or with PCI express. Receiver  536  receives signals carrying data from channel  510 . The data is decoded into appropriate codewords using FEC decoder  526  to provide information to host system  516 . If the data contains more than a predetermined number of errors for correction by FEC decoder  526 , an integrity control  546  requests retransmission using ARQ techniques. In an embodiment, FEC decoder  526  and integrity control  546  operate above a physical layer in a manner similar to one or more embodiments described herein. FEC decoder  526  and integrity control  546  may be configured as part of receiver  536  or external to receiver  536  and may provide the information upon decoding to host system  516 . 
     The network nodes  504 ,  506  each may represent processing systems having a physical layer (PHY) entity arranged to operate in accordance with 10GBase-T as defined by the IEEE 802.3an series of standards, for example. The 10GBase-T PHY may interface with, for example, a 10G media access control (MAC) and Gigabit Media Independent Interface (XGMII) in the IEEE architecture. The 10GBase-T PHY may include part of a network interface card (NIC), for example. Nodes  504 ,  506  may include any processing system and/or communications device suitable for use with a 10GBase-T device. For example, nodes  504 ,  506  may be implemented as a pair of switches, a pair of routers, a pair of servers, a switch and a router, a switch and a server, a server and a router, and so forth. In addition, nodes  504 ,  506  also may be part of a modular system in which 10GBase-T is the high-speed connection for the system. In an embodiment, network nodes  504 ,  506  may be arranged such that host system  514  and host system  516  are configured as a single host system. Further examples for nodes  504 ,  506  may include high-end servers, supercomputers, clusters, grid computing, workgroup switch uplinks, aggregation uplinks, storage systems, and so forth. The embodiments are not limited in this context. 
       FIG. 6  illustrates a block diagram of an embodiment of a communication network  600  having a system  601  and a system  602  communicating through communication channel  608 . System  602  includes a forward error correction module  605  with a high code rate in a data link layer  630 - 2  to encode information. System  601  includes a forward error correction module  620  in a data link layer  630 - 1  to decode data and an integrity control  610  in the data link layer  630 - 1  to generate automatic repeat requests. Data link layer  630 - 1  is the data link layer of communication network  600  relative to system  601 , while data link layer  630 - 2  is the data link layer of communication network  600  relative to system  602 . Similarly, physical layer  640 - 1  is the physical layer of communication network  600  relative to system  601 , while physical layer  640 - 2  is the physical layer of communication network  600  relative to system  602 . 
     Communication channel  608  couples system  601  and system  602  to provide a medium for propagating information between system  601  and  602 . In an embodiment, communication channel  608  may be a full-duplex channel. Communication channel  608  may include, but is not limited to, a fiber optic channel, a wired channel, a channel for reading data stored on a memory unit, or a wireless channel. Additionally, embodiments for decoding and encoding may be adapted for use with any protocol for transmission over any communication channel. 
     System  602 , in addition to FEC encoder module  605 , may include a split unit  615  to split packets, a buffer  625 , a confirmations and retransmissions unit  655 , a demodulation unit  645 , and a coded modulation unit  635  from which data is transmitted onto communication channel  608 . FEC encoder module  605  may be adapted to encode information with a code rate of 0.98 or better. In an embodiment, FEC encoder module  605  has a code rate of about 0.99. Codewords generated by FEC encoder module  605  may be provided to coded modulation unit  635 . At coded modulation unit  635 , forward error correction techniques may be applied on physical layer  640 - 2 . 
     System  601 , in addition to integrity control  610  and FEC module  620 , may include a combine unit  615  to combine data from packets, a coded modulation unit  670  to send confirmations and repeat requests to systems with which system  601  is communicating, and a demodulation unit  660  to receive signals from communication channel  608 . At coded modulation unit  670 , forward error correction techniques may be applied on physical layer  640 - 1  to repeat requests and confirmations sent to communication channel  608 . 
     FEC module  620  may be adapted to decode codewords having a number of errors less than an error threshold. In an embodiment, the error threshold is set to two errors. In an embodiment, the error threshold is set to one error. The error threshold is not limited to two errors or less but may be set to appropriate values for the application in which the embodiment is adapted. Integrity control  610  may be adapted to implement ARQ techniques for errors that remain after decoding using FEC module  605  or if FEC module  605  reports an error regarding the data. In an embodiment, the error threshold may be stored in software as a set of values that may be applied at different times in operation. 
     Various embodiments for communication network  600 , system  601 , and system  602  may be realized. Communication network  600  may be a land based network using optical fibers, coaxial cable, or wires as a medium for the communication channels between various nodes of communication network  600 . Each node of communication network  600  configured as a land based network or as a wireless based network may contain a version of system  602  and/or a version of system  601  or a system that is a combination of system  602  and system  601 . Communication network  600  may be realized as a wireless network in which systems  602  and  601  are configured as part of a node of communication network  600  or as part of a wireless receiving device that receives signals from the nodes of communication network  600 . System  601  and system  602  may be configured as part of, but not limited to, network components such as a stationary wireless devices and base stations and may be configured as part of, but not limited to, wireless receiving devices such as portable wireless devices, handheld communication devices, computers, and laptop computing devices. Though not shown, systems  601  and  602  configured in a wireless communication system  600  may include antennas for transmitting and receiving signals. The error handling schemes and apparatus do not limit the type or configuration of supporting components such as antennas in systems  601 ,  602 . In an embodiment, a substantially omnidirectional antenna may be utilized. 
       FIG. 7  demonstrates an embodiment of a joint operation of forward error correction and automatic repeat request with respect to automatic repeat request only with respect to operation in the data link layer. Joint FEC and ARQ operation is shown by curve  705 , while ARQ only operation is shown by curve  710 . At a signal-to-noise ratio (SNR) of 37 dB, the average number of retransmissions of ARQ only is about 2.75×10 −3 , while the average number of retransmissions of joint FEC and ARQ operation is about 1.8×10 −3 . With transmission of a file having a file length of 1 Mb, the gain from joint FEC and ARQ on the data link layer is about 2 μs. 
     Various embodiments or combination of embodiments for apparatus and methods for joint operation of forward error correction techniques and automatic repeat request techniques above a data link layer to decode signals, as described herein, can be realized in hardware implementations, software implementations, and combinations of hardware and software implementations. Various embodiments for apparatus and methods for encoding information on a data link layer using forward error correction with a code rate of 0.98 or higher, as described herein, can be realized in hardware implementations, software implementations, and combinations of hardware and software implementations. Various embodiments include both joint operation of forward error correction techniques and automatic repeat request techniques above a data link layer for decoding and FEC encoding with a code rate of 0.98 or higher. These implementations may include a computer-readable medium having computer-executable instructions for performing an embodiment of a joint operation of forward error correction techniques and automatic repeat request techniques above a data link layer and/or using an embodiment for encoding information on a data link layer using forward error correction with a code rate of 0.98 or higher. The computer-readable medium is not limited to any one type of medium. The computer-readable medium used will depend on the application using an embodiment of the joint FEC/ARQ operation and/or FEC encoding of information at a code rate of 0.98 or higher in a data link layer. In an embodiment, a processor coupled to a receiver and/or transmitter may utilize various forms of memory to which it is coupled and the computer-readable medium to direct joint FEC/ARQ decoding operation and/or FEC encoding of information at a code rate of 0.98 or higher in a data link layer for data transmission in a channel from a physical layer. In an embodiment, the memory may store parameters used in the various embodiments as discussed herein. 
       FIG. 8  illustrates a block diagram of an embodiment of a system  800  having a forward error correction module to decode data and an integrity control to generate automatic repeat requests, where the decoding forward error correction module and the integrity control to generate automatic repeat requests are configured above the physical layer according to various embodiments. System  800  may include a high code rate forward error correction module in a data link layer to encode information. Such an encoder may be realized as a FEC encoder with a code rate of about 0.98 or higher. System  800  includes a controller  810 , an electronic device  820 , and a bus  830 , where bus  830  provides electrical conductivity between controller  810  and electronic device  820 , and between controller  810  and communication unit  840 . An embodiment may include an additional peripheral device or devices  860  coupled to bus  830 . Bus  830  may be compatible with PCI or with PCI express. In an embodiment, communication unit  840  may include a network interface card. In an embodiment, communication unit  840  may a communications device suitable for use with a 10 GBase-T device. In a wireless embodiment, communication unit  840  is coupled to an antenna  850 . In an embodiment, antenna  850  may be a substantially omnidirectional antenna. Electronic system  800  may include, but is not limited to, information handling devices, wireless systems, telecommunication systems, fiber optic systems, electro-optic systems, and computers. 
     In an embodiment, controller  810  is a processor. In an embodiment, electronic device  820  is a memory that stores computer executable instructions to perform FEC techniques and ARQ techniques above a physical layer of a communication network to which system  800  is coupled with respect to data received by system  800 . Peripheral devices  860  may include displays, additional storage memory, or other control devices that may operate in conjunction with controller  810 . Alternatively, peripheral devices  860  may include displays, additional storage memory, or other control devices that may operate in conjunction with controller  810 , communication unit  840 , and/or electronic device  820 . 
     Embodiments for a joint FEC and ARQ scheme operating above a physical layer may be adapted to be used in any system operating with a communication channel. The communication channel may be part of a land based communication network or a wireless communication network. Indeed, embodiments may well be implemented as part of any wireless system using multi-carrier wireless communication channels (e.g., orthogonal frequency-division multiplexing (OFDM), discrete multi-tone modulation (DMT), etc.), such as may be used within, without limitation, a wireless personal area network (WPAN), a wireless local area network (WLAN), a wireless metropolitan area network (WMAN), a wireless wide area network (WWAN), a cellular network, a third generation (3G) network, a fourth generation (4G) network, a universal mobile telephone system (UMTS), and similar communication systems. 
     Various embodiments of joint FEC and ARQ operation above the physical layer provide method and apparatus that decrease message delay due to minimization in the number of retransmission. The various embodiments of joint FEC and ARQ also provide overall error probability approximately equal to zero due to matched retransmission. These various embodiments allow the physical layer error correction to be kept “as is” without more complications, since such configurations reduce or eliminate the need for the physical layer on networks such as 10G Ethernet to be errorless. Further, lowering the number of automatic repeat requests allows an increase in overall data transfer rate in spite of using additional forward error correction. Using a FEC encoder with a code rate about 0.98 or higher, needed error correction may be performed on the MAC layer that avoids retransmission of long packets. 
     Increasing the quality of transmission by using the error-correcting codes at levels above the physical layer tends toward the optimization of the coding system, i.e., codes parameters, multilevel coded modulation properties, etc. Coded modulation scheme on the physical level may be selected in order to provide non-uniform distribution of errors, as it is done in PAM using LDPC coded modulation. However, the distance between groups of errors may be made larger. For example, for joint FEC and ARQ operation, the result of LDPC coded modulation may include frames in which 2-3 errors may be the most probable and other frames may either contain no errors at all or contain a very large number of errors (100-150 and more). Larger distances between groups of errors may lead to better results of joint FEC and ARQ operation. The trade-off between FEC and ARQ can be used to operate on low SNRs. If the delay time is not critical, a significant gain in power consumption is possible by increasing the delay and properly selecting codes on the physical layer and above. Also, other coded modulation schemes on the physical layer may be used to provide non-zero error probability on the physical layer and large distances between groups of errors. The applications of joint FEC and ARQ operation may be used not only on 10G Ethernet networks, but also wireless communications in one-to-one transmission modes and also in one-to-many transmission mode (broadcast, multicast). 
     Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of embodiments of the present invention. It is to be understood that the above description is intended to be illustrative, and not restrictive, and that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Combinations of the above embodiments and other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the present invention includes any other applications in which embodiment of the above structures and fabrication methods are used. The scope of the embodiments of the present invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.