Latency and networking aspects of adaptive modems over slow indoors Rayleigh fading channels

Torrance, J.M.; Hanzo, Lajos

doi:10.1109/25.775372

Cited by 29 publications

(19 citation statements)

References 34 publications

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“…Due to lack of space these issues are beyond the scope of this contribution and we have assumed zero-delay perfect AQAM mode signaling. For a deeper discussion on this topic the reader is referred to [4], while the associated co-channel interference aspects were treated in [34].…”

Section: Turbo-coded Rbf-equalized -Qam Performance Resultsmentioning

confidence: 99%

“…Furthermore, we used the shorthand and . By introducing the Jacobian logarithm, every weighted summation of two exponential operations in (2) is substituted according to (4) by an addition, the subtraction , the table look-up and a operation, thus reducing the computational complexity. The computational complexity of the logarithmic RBF DFE, employing the Jacobian algorithm, with feedforward order of , feedback order of and having hidden RBF nodes per equalized output sample, is given in Table I.…”

Section: Jacobian Logarithmic Rbf Equalizermentioning

confidence: 99%

“…A DAPTIVE quadrature amplitude modulation (AQAM) was originally proposed by Webb and Steele [1] and it was further developed by Sampei et al [2], Goldsmith et al [3], and Torrance et al [4] in the context of nondispersive channels. Wong et al [5] extended these contributions to dispersive wideband channels with the aid of a burst-by-burst (BbB)-adaptive Kalman filtered AQAM scheme.…”

Section: Introductionmentioning

confidence: 99%

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Burst-by-burst adaptive turbo-coded radial basis function-assisted decision feedback equalization

Yee

Liew

Hanzo

2001

IEEE Trans. Commun.

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Abstract-The performance of the proposed radial basis function (RBF) assisted turbo-coded adaptive modulation scheme is characterized in a wideband channel scenario. We commence by introducing the novel concept of the Jacobian RBF equalizer, which is a reduced-complexity version of the conventional RBF equalizer. Specifically, the Jacobian logarithmic RBF equalizer generates its output in the logarithmic domain and hence it can be used to provide soft outputs for the turbo-channel decoder. We propose using the average magnitude of the log-likelihood ratio (LLR) of the bits in the received transmission burst before channel decoding as the channel quality measure for controlling the mode-switching regime of our adaptive scheme. [7]. However, there is little information concerning its potential in either BbB AQAM or in forward error correction (FEC)-coded scenarios, despite the advantageous interactions of RBF-aided DFE BbB AQAM in conjunction with turbo FEC, which were demonstrated in our preliminary work [8]. Hence in this contribution, we set out to document these interactions. IndexThe symbol-spaced channel output can be defined by (1) where ; channel impulse response (CIR); channel's input sequence; noiseless channel output.Paper approved by C. Schlegel, the Editor for Coding Theory and Techniques of the IEEE Communications Society. Manuscript received April 5, 2000; revised March 20, 2001. This work was supported by the EPSRC, the U.K., and the Commission of the European Communities, Brussels, Belgium.The authors are with the Department of Electronics and Computer Science, University of Southampton, Highfield Southampton SO17 1BJ, U.K. (e-mail: lh@ecs.soton.ac.uk).Publisher Item Identifier S 0090-6778 (01) [17] promoted the employment of RBF based equalizers, which exhibit a structure identical to that of the optimal Bayesian symbol-decision based equalizer. Therefore, RBF equalizers can rely on optimal detection theory [18]. In this contribution, we use a decision feedback assisted RBF equalizer, which involves its previous decisions for either RBF subset center selection [17] or space translation [19], [20], in order to reduce its computational complexity. Both versions of the DFE realize the same optimal solution, but the space translation based version [19], [20] requires less storage for the RBF centers, since the centers corresponding to different decision feedback vectors are equivalent in the translated space [19], [20]. Therefore the latter version is preferred in hardware implementations.BbB AQAM schemes [21] employ a higher-order modulation scheme in a certain transmission burst, when the channel quality is favorable, in order to increase the throughput and conversely, a more robust, lower-order modulation scheme is utilized in those transmission bursts, where the instantaneous channel quality drops [1]. The performance benefits of the RBF DFE [17] have been documented in the context of AQAM over dispersive wideband mobile channels in [22], [23], demonstrating that a certain target bit error rate ...

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Section: Turbo-coded Rbf-equalized -Qam Performance Resultsmentioning

confidence: 99%

Section: Jacobian Logarithmic Rbf Equalizermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Burst-by-burst adaptive turbo-coded radial basis function-assisted decision feedback equalization

Yee

Liew

Hanzo

2001

IEEE Trans. Commun.

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“…Publisher Item Identifier S 1089-7798(00)07659-6. where is the symbol interval, which is related to the bit duration by where represents the number of bits per symbol, the quadrature amplitudes and range over the set of , in which represents the minimum Euclidean distance of constellation points, while can be computed according to [5]: (2) where represents the average energy per bit. Throughout, we will restrict our considerations to Gray coded bit mapping [1].…”

mentioning

confidence: 99%

“…-ary QAM ( -QAM) is a bandwidth efficient scheme, which has been employed for digital video broadcasting (DVB) [1], while adaptive -QAM has been applied for high-speed data transmission over fading channels [2], [3]. Conventionally, the bit error rate (BER) computation of -QAM has been performed by either calculating the symbol error probability first [4], [5] or simply estimating it using lower/upper bounds [4], [6].…”

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confidence: 99%