Optimisation of switching levels for adaptive modulation in slow Rayleigh fading

Torrance, J.M.; Hanzo, Lajos

doi:10.1049/el:19960799

Cited by 106 publications

(55 citation statements)

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“…We also assume that the receiver has perfect knowledge of the modulation mode used in its received transmission burst. In a practical system, the transmitter notifies the receiver of all the AQAM mode changes and control symbols must be used for conveying the modulation mode employed by the transmitter to the receiver, for example using the regime of [35].…”

Section: B Simulation Resultsmentioning

confidence: 99%

“…When aiming for virtually error-free communications, an even more conservative LLR threshold has to be chosen, in order not to precipitate a plethora of transmission errors, even at the cost of thereby reducing the achievable BPS throughput of the system. Recent studies of the SNR-dependent AQAM switching thresholds can be found in [35]- [37]. Our future research will explore the feasibility of finding a real-time adaptive learning algorithm for providing optimized switching thresholds for the AQAM scheme online.…”

Section: B Simulation Resultsmentioning

confidence: 99%

“…The target BER requirement can be met by obtaining the average frame LLR magnitude of each modulation mode corresponding to the estimated channel quality and by activating the specific AQAM mode satisfying this target BER. In adapting the modulation mode, an AQAM mode signaling regime has to be implemented in order to harmonize the operation of the transmitter and receiver, for example using the regime proposed in [35].…”

Section: A System Overviewmentioning

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: B Simulation Resultsmentioning

confidence: 99%

Section: B Simulation Resultsmentioning

confidence: 99%

Section: A System Overviewmentioning

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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“…Similar schemeshave been investigated by Suzuki and Morinaga [4] as well as Chau and Goldsmith [5]. It has been shown [6] that o ptimisation may be employed for example to ensure that BERs of 1 10 2 and 1 10 4 are maintained for average channel SNRs in the range of 0 to 50 dB over a Rayleigh fading c h annel, if the switching levels l1, l2, l3 and l4 are assigned as shown in Table 1.…”

Section: Introductionmentioning

confidence: 95%

“…Steele and W e bb [1] proposed adaptive m o d ulation for mobile fading c h annels and recently there has been considerable interest in its performance [2]- [6]. The principle of operation is to employ t h e m o s t a p propriate T ransmission Scheme (TS) in order to maintain a certain target bit error rate (BER) performance.…”

Section: Introductionmentioning

confidence: 99%