D. Chase, "Code combining---A maximum likelihood decoding approach for combining an arbitrary number of noisy packets," IEEE Trans. Commun., vol. 33, no. 5, pp. 385--393, May 1985.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....or more packets have been received. There are, however, other methods that yield better performance for soft decision decoding. The concept of packet combining was first suggested by [24] There are two major types of packet combining, diversity combining, 24] 25] 23] and code combining, [26], 27] 28] Diversity combining is in general simple to implement, but does often not perform as well as code combining. The majority voting schemes for hard decision decoding is a typical diversity combining scheme. Individual symbols from multiple identical copies of a packet are combined to ....

....or more packets have been received. There are, however, other methods that yield better performance for soft decision decoding. The concept of packet combining was first suggested in [24] There are two major types of packet combining, diversity combining, 24] 25] 23] and code combining, [26], 27] 28] Diversity combining is traditionally implemented before the decoder on a symbol by symbol basis whereas code combining is implemented within the decoder based on code word by code word combining. Diversity combining is in general simpler to implement, but it is often a sub optimal ....

D. Chase, "Code combining - a maximum-likelihood decoding approach for combining an arbitrary number of noisy packets," IEEE Transactions of Communications, vol. 33, no. 5, pp. 385-393, May 1985.

....In the IR scheme, the server can incrementally increase the amount of transmitted redundancy in response to negative acknowledgements fed back from the client. Hence the IR scheme is adaptive to the error characteristics of the network. Furthermore, the scheme uses the code combining principle [22, 23] to ensure that none of the received redundancy information is discarded, which makes it appealing from a bandwidth efficiency viewpoint. Optimal use of the IR transmission scheme is determined by an optimization procedure known as the Iterative Sensitivity Adjustment (ISA) algorithm [24, 25] ....

D. Chase, "Code combining -- a maximum likelihood decoding approach for combining an arbitrary number of noisy packets," IEEE Trans. Communications, vol. Comm-33, pp. 385--393, May 1985.

....but, when an error does occur, more bits will have to be repeated. A simplified analysis of these trade offs in [ZHG97] suggest that there is a limit on the maximum codeword length one should use. This analysis does not consider more elaborate hybrid ARQ strategies such as code combining [Cha85] or incremental redundancy [LY83] which do not disregard a codeword which is in error. We will give a simple model for such strategies in Sect. 4.3. 4. Adapting to channel fades: As in the above example, suppose that data is arriving at a constant rate of R and that fixed length block codes ....

D. Chase. Code-combining--a maximum likelihood decoding approach for combining an arbitary number of noisy packets. IEEE Trans. Commun., COM-33(5):385--393, May 1985.

....redundancy protocols have the potential to yield simple and efficient error correction for slotted Gaussian multiple access channels. In particular it is demonstrated that it is possible to achieve higher throughput with incremental redundancy pro tocols than slotted ALOHA or packet combining [3] protocols. However, a challenging issue is to find practical codes with high performance and low complexity suitable for incremental redundancy protocols. In contrast to conventional ARQ techniques, incremental redundancy protocols require channel codes that are rate compatible. Rate compatible ....

D. Chase, "Code combining - a maximumlikelihood decoding approach for combining and arbitrary number of noisy packets," IEEE Transactions on Communications, vol. 33, pp. 385- 393, May. 1985.

....times. In section 8 we introduce the concept of limiting the number of block retransmission attempts. Finally, in Section 9 we present numerical results and comment on how block size selection effects system performance. 2. TYPE II HARQ Type II HARQ [14] is a special case of code combining [5], and an extension of automatic repeat request (ARQ) The fundamental principle was first proposed in [1] where it was suggested that Reed Solomon codes [6] could be used to code a message of m symbols and c cyclic redundancy check (CRC) bits, producing a codeword containing r c redundancy bits ....

D. Chase, "Code combining -- a maximum-likelihood decoding approach for combining an arbitrary number of noisy packets," IEEE Transactions on Communications, vol. COM-33, no. 5, May 1985, pp. 385-393.

....of one packet are combined by adding the corresponding soft values at bit level. Different types of HARQ combining exist, and in general, a trade off between implementation effort and buffer requirements on the one hand and decoding gain on the other hand can be achieved. Chase Combining [6] has been proposed, since it requires minimum complexity and buffer. Initial transmission and retransmission are identical. Chase Combining offers time diversity and soft combining gain (i.e. the energy accumulation effect for each bit) Additional decoding gain is achieved if the ....

D. Chase, "Code Combining -- A Maximum-Likelihood Decoding Approach for Combining an Arbitrary Number of Noisy Packets," D #U...h+##8'#, vol. 33, no. 5, pp. 385-393, May 1985,

....or more of the other sub blocks is transmitted. Code Block A1 Channel Encoder e.g Turbo encoder Coded Sub Blocks A11 A12 A13 A14 NEW Sub block RETX Sub block Figure 1. Code block and sub block formation. The two main combining schemes considered for HSDPA are Chase combining [4] (Type III with one redundancy version) and Incremental Redundancy (IR) either Type II or III) Chase combining involves the retransmission of the same coded sub block in each retransmission. In IR, instead of simple repetitions, additional redundancy (parity bits) information may be transmitted ....

D. Chase, Code combining: A Maximum-Likelihood Decoding Approach for Combining an Arbitrary Number of Noisy Packets, IEEE Transactions on Communications, May 1985.

....due to the estimation errors of radio link conditions or in control information signalling. In the standard discussion of HSDPA, two types of HARQ are compared from the viewpoint of the achievable throughput performance and complexity such as buffer memory size: Type I HARQ with packet combining [9] (simply Chase combining hereafter) and Type II HARQ [10] incremental redundancy hereafter) Although the throughput in HSDPA based on the W CDMA air interface with a 5 MHz bandwidth has been extensively investigated, the effect of HARQ in the broadband channel using, for example, a 100MHz ....

D. Chase, "Code combining -- a maximum-likelihood decoding approach for combining an arbitrary number of noisy packets," IEEE Trans. Commun., vol. 33, no. 5, pp. 385-393, May 1985.

....of frames, extending the frame transmission model to calculate packet transmission times. Finally, in Section 8 we present numerical results and comment on how block sizes should be selected to maximise system performance. 2. TYPE H HARQ Type 1I HARQ [14] is a special case of code combining [5], and an extension of automatic repeat request (ARQ) The fundamental principle was first proposed in [1] where it was suggested that Reed Solomon codes [6] could be used to code a message of m symbols and c cyclic redundancy check (CRC) bits, producing a codeword containing r c redundancy bits ....

....block as required. In this paper, we will focus on modelling Type II HARQ schemes based on MDS codes. 3. THE TYPE II HARQ MODEL We consider a type 1I HARQ scheme based on coding the message and CRC bits with code rate of Although MDS codes provide the ability to k detect up to dmin 1 errors [5], the system does not rely on this feature. The robustness of the system is increased by appending a length c CRC code to the original message, reducing the probability of an undetected error to 2 c [8] The codeword is then punctured leaving an information block, of length m c, and two blocks ....

D. Chase, "Code combining - a maximum-likelihood decoding approach for combining an arbitrary number of noisy packets," IEEE Transactions on Communications, vol. COM-33, no. 5, May 1985, pp. 385-393.

....to the best knowledge of the authors. Therefore, this paper presents the performance of the PER and that for the packet throughput employing CS CDMA, i.e. very low rate turbo coding, associated with Type I hybrid ARQ with packet combining, i.e. Chase combining (Chase combining hereafter) [11] in a multipath Rayleigh fading channel, and compares them to those when employing the conventional DSCDMA using OVSF code based bandwidth spreading. The rest of the paper is organized as follows. First, Section II describes a CDMA system using the CS CDMA and DS CDMA. Section III describes the ....

D. Chase, "Code combining -- a maximum-likelihood decoding approach for combining an arbitrary number of noisy packets, " IEEE Trans. Commun., vol. 33, pp. 385-393, May 1985. (a) f D = 5Hz Fig. 8. ThroughputPerformances in 2-path channel (b) f D = 80Hz (a) f D = 5Hz Fig. 9. Throughput Performances with antenna diversity

....(2. 4) If decoding is still not successful, several options are available, including i) passing control to a higher order protocol, ii) repeat the whole procedure with differentvalues of N , M , and or P,or iii) repeat the rate 1=N code L k times, and combine it with the already transmitted code [4]. Two QOS measures that have been computed to quantify the performance of this hybrid ARQ FEC scheme are, i) the average throughput, and ii) the probability that a frame containing n information bits is not decoded correctly. If we assume that the protocol stops with the rate 1=N code in step ....

D. Chase, Code Combining-A Maximum Likelihood Decoding Approach for Combining an Arbitrary Number of Noisy Packets, IEEE Trans. Commun., 33(4)(1985), 385-393.

....then a retransmission is requested. Each subsequent retransmission is decoded independently of the prior transmissions. A Type II system uses incremental redundancy retransmissions and a code combining method to further increase the system throughput. Code combining can take a variety of forms [2], 3] 4] Retransmission requests in a type II system are often generated by using an error detecting code as an outer code embedded in an inner error correcting code. Another approach to generate retransmission request is by using the soft decoding information of decoder as a reliability ....

D. Chase. Code combining--a maximum likelihood decoding approach for combining an arbitrary number of noisy packets. IEEE Trans. Commun., COM-33:385--393, May 1985.

....of 14 . One conclusion of the study is that the number of sources in a network using FEC may have to be limited in order for the effect to be significant. 2.2. 2 Hybrid FEC ARQ Many hybrid schemes in which forward error correction is combined with the use of retransmissions have been studied [12, 32, 49], though only in the context of channel efficiency, and not for delay constrained communication. Under these schemes the receiver uses the parity bits in forward error correction to recover from losses, but when there are too many errors a retransmission is requested from the transmitter. The ....

....receiver uses the parity bits in forward error correction to recover from losses, but when there are too many errors a retransmission is requested from the transmitter. The retransmission may be the original message [32] or additional parity bits that will allow recovery of the original message [12]. 18 Hybrid schemes can be effective in reducing the bandwidth consumed through overcoding since larger losses can be recovered through retransmissions. Overall performance of the error recovery mechanisms as measured in terms of average throughput is generally superior to pure FEC or pure ARQ ....

D. Chase. Code Combining--- A Maximum-Likelihood Decoding Approach for Combining an Arbitrary Number of Noisy Packets. IEEE Transactions on Communication, 33(5):385--393, May 1985.

....a fixed rate forward error correcting(FEC) code and discards erroneous packets if they contain uncorrectable errors. Modified FEC ARQ schemes use rate adaptive coding techniques, which send incremental redundancy in each retransmission and combine all received packets to make a joint re decoding[19, 20]. Recent advances in turbo coding techniques, originally proposed by Berrou et al. 21] in 1993, enable us to achieve error performance approaching Shannon limit on AWGN channel. Application of punctured turbo codes for redundancy retransmission in ARQ system has been studied in[22, 23] This ....

....rate can be made to maximize the throughput. For example, when L = 0:5, the optimal code is RS(54,34) for voice frame and RS(83,53) for ATM cell, respectively; when L = 3, turbo coding without RS coding system is the best choice for both data sources. Comparison with average code combining(ACC)[19], which retransmits the same information copy then averages up all received copies, and standard ARQ, is also shown in Fig.66(a) It is observed that the proposed system quadruples the maximum throughput of a standard FEC ARQ system. Considerable gain over average code combining is also obtained ....

D. Chase, "Code combining -- a maximum-likelihood decoding approach for combining an arbitrary number of noisy packets," IEEE Transactions on Communications, vol. COM-33, no. 5, pp. 385--393, May 1985.

.... [6] and Lin and Yu [7] Other combined ARQ FEC schemes have been presented by Lin and Costello [8, 9] Among the more recent contributions, the technique of combining all the received copies of a packet in order to obtain useful throughput at very high channel error rates appears very interesting [10, 11, 12, 13, 14]. A significant amount of work has been done on hybrid ARQ FEC schemes using both convolutional coding and sequential decoding [15, 16, 17, 18] This paper follows the line of research that was opened up by Yu and Lin [19, 20] and by Wang and Lin [21] This line is characterized by a scheme that ....

D. Chase, "Code combining: A maximum-likelihood decoding approach for combining an arbitrary number of noisy packets," IEEE Trans. Commun., vol. COM-33, pp. 385-393, May 1985.

....adjust the FEC overhead to that actually required by the channel. 15, 16, 20, 24] What if the receiver cannot decode the packet even after we send all the rows One possibility is to send the whole thing again and to use code combining at the receiver to add the two transmissions before decoding. [23] For example, if we send all of the symbols belonging to a rate 1 2 code twice, we have effectively switched to a rate 1 4 code. Although this particular rate 1 4 code provides no additional coding gain over the original rate 1 2 code (since the retransmissions are identical) adding the two ....

David Chase, "Code Combining - A Maximum-Likelihood Decoding Approach for Combining an Arbitrary Number of Noisy Packets", IEEE Transactions on Communications, Vol COM-33, No 5, May 1985, p. 385. -12-

....and error correction. The receiver corrects a certain number of errors using an error correction code (like FEC) but when there are too many errors the receiver uses the error detection code to request retransmission (like ARQ) A variation on the hybrid schemes [10 13] is code combining [14]. Here, the original message is generated just like in a pure ARQ scheme, with only enough extra parity bits transmitted to allow the receiver to perform error detection; when a retransmission is requested, however, the transmitter sends parities from an FEC code instead of repeating the message. ....

....can also be used to improve latency by applying it just to the ECB headers. This increases the probability of the receiver getting the header, allowing it to send back a NAK if the data was corrupted. 11. CODE COMBINING When using ARQ with FEC, it is possible to retransmit using code combining [14]. If insufficient redundancy was used the first time the message was sent, more information is needed if an error free message is required. Assuming a return channel exists, a request for retransmission (ARQ) can be made. However, retransmitting the whole block is often undesirable. If only a ....

D. Chase, "Code Combining - A Maximum-Likelihood Decoding Approach for Combining an Arbitrary Number of Noisy Packets," IEEE Tran. on Communications, Vol.33, No.5, pp.385-393, May 1985.

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D. Chase, "Code combining---A maximum likelihood decoding approach for combining an arbitrary number of noisy packets," IEEE Trans. Commun., vol. 33, no. 5, pp. 385--393, May 1985.

No context found.

D. Chase, "Code-combining - a maximum likelihood decoding approach for combining an arbitrary number of noisy packets," IEEE Trans. on Commun., vol. 33, May 1985.

No context found.

D. Chase, " Code combining- A maximum likelihood decoding approach for combining an arbitrary number of noisy packets," ," IEEE Transactions on Communications, Vol. 33, pp. 385-393, May 1985.

No context found.

D. Chase, "Code Combining-A Maximum-Likelihood Decoding Approach for Combining an Arbitrary Number of Noisy Packets," IEEE Transactions on Communications, vol. COM-33, no. 5, pp. 385-393, May 1985.

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