A Cascadable Pragmatic Block Decoding Algorithm Exploiting Channel Measurement Information

The complexity of algorithms to perform soft decision decoding on block codes has impeded their inclusion in practical systems. A well-known class of algorithms for decoding block codes utilizing channel measurement information along with the algebraic properties of the code are the Chase algorithms.1 In this paper a decoding method similar to Chase\u27s third algorithm is presented. However, in this method, a single test pattern or alternate codeword makes up one stage of the decoder. The method uses information from the previous decoding(s) to assist in generating a test pattern. This single stage ‘Second Chance Algorithm’ can then be extended to a ‘Third Chance Algorithm’ (and beyond) to enhance performance. The method does not invoke the hard decision decoder as often as the Chase algorithms

A Planar Approximation for the Least Reliable Bit Log-likelihood Ratio of 8-PSK Modulation

The optimum decoding of component codes in block coded modulation (BCM) schemes requires the use of the log-likelihood ratio (LLR) as the signal metric. An approximation to the LLR for the least reliable bit (LRB) in an 8-PSK modulation based on planar equations with fixed point arithmetic is developed that is both accurate and easily realizable for practical BCM schemes. Through an error power analysis and an example simulation it is shown that the approximation results in 0.06 dB in degradation over the exact expression at an E(sub s)/N(sub o) of 10 dB. It is also shown that the approximation can be realized in combinatorial logic using roughly 7300 transistors. This compares favorably to a look up table approach in typical systems

Planar Approximation for the Least Reliable Bit Log-Likelihood Ratio of 8-PSK Modulation

The optimum decoding of component codes in block coded modulation (BCM) schemes requires the use of the log-likelihood ratio (LLR) as the signal metric. An approximation to the LLR for the least reliable bit (LRB) in an 8-PSK modulation based on planar equations with fixed-point arithmetic is developed that is both accurate and easily realisable for practical BCM schemes. Through an error power analysis and an example simulation it is shown that the approximation results in less than 0.06 dB in degradation over the exact expression at an Es/N0 of 10 dB. It is also shown that the approximation can be realised in combinatorial logic using roughly 7300 transistors. This compares favourably to a look-up table approach in typical systems

An Adaptive Scheme for Admission Control in ATM Networks

This paper presents a real time front-end admission control scheme for ATM networks. A call management scheme which uses the burstiness associated with traffic sources in a heterogeneous ATM environment to effect dynamic assignment of bandwidth is presented. In the proposed scheme, call acceptance is based on an on-line evaluation of the upper bound on cell loss probability which is derived from the estimated distribution of the number of calls arriving. Using this scheme, the negotiated quality of service will be assured when there is no estimation error. The control mechanism is effective when the number of calls is large, and tolerates loose bandwidth enforcement and loose policing control. The proposed approach is very effective in the connection oriented transport of ATM networks where the decision to admit new traffic is based on thea priori knowledge of the state of the route taken by the traffic

Pragmatic Approach to Soft-Decision Decoding of Linear Block Codes

The complexity of algorithms to perform soft-decision decoding on block codes has impeded their use in practical systems. The authors investigate correlation decoding along with hard-decision decoding. The proposed method uses a hard-decision decoder that decodes to a codeword. Although this codeword may be in error, it is usually close in Hamming distance to the transmitted codeword. Correlation is then performed on only a small set of `nearby\u27 codewords. This pseudo maximum likelihood (PML) decoding method can approach the performance of true correlation decoding with a significant reduction in complexity

Pragmatic Approach to Soft-Decision Decoding of Linear Block Codes

The complexity of algorithms to perform soft-decision decoding on block codes has impeded their use in practical systems. The authors investigate correlation decoding along with hard-decision decoding. The proposed method uses a hard-decision decoder that decodes to a codeword. Although this codeword may be in error, it is usually close in Hamming distance to the transmitted codeword. Correlation is then performed on only a small set of `nearby\u27 codewords. This pseudo maximum likelihood (PML) decoding method can approach the performance of true correlation decoding with a significant reduction in complexity

A Cascadable Pragmatic Block Decoding Algorithm Exploiting Channel Measurement Information

The complexity of algorithms to perform soft decision decoding on block codes has impeded their inclusion in practical systems. A well-known class of algorithms for decoding block codes utilizing channel measurement information along with the algebraic properties of the code are the Chase algorithms.1 In this paper a decoding method similar to Chase\u27s third algorithm is presented. However, in this method, a single test pattern or alternate codeword makes up one stage of the decoder. The method uses information from the previous decoding(s) to assist in generating a test pattern. This single stage ‘Second Chance Algorithm’ can then be extended to a ‘Third Chance Algorithm’ (and beyond) to enhance performance. The method does not invoke the hard decision decoder as often as the Chase algorithms

Practical 8-PSK Block-Coded Modulation With Convolutional Codes and Soft Decision Block Codes for Packet Networks

The design and performance of a class of practical rate 2/3, 8-PSK block-coded modulation (BCM) (also referred to as multilevel modulation codes) schemes are presented. These BCM schemes utilise both convolutional codes and block codes, and have block lengths that are matched with relatively short packet lengths to satisfy requirements in packet-wireless networks. Decoding issues such as optimum signal metrics and soft-decision decoding of block codes are addressed. The performance is evaluated and simulated. It is found that these BCM schemes exhibit a coding gain comparable to 16, 32 and 64 state Ungerboeck (1982) TCM codes, but require less complexity to decode