Variable rate QAM for mobile radio

Webb, William; Steele, R.

doi:10.1109/26.392965

Cited by 375 publications

(178 citation statements)

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“…Based on the observation that the instantaneous channel quality expressed in terms of SINR is time-variant in wireless systems, such burst-by-burst adaptive multimode, multilevel modems were invented by Steele and Webb at the University of Southampton in [80], [81], and [28] for slowly fading wireless pedestrian channels, where the channel fluctuations were slow with respect to the transmission burst length. Their work spawned further research in recent years [87]- [95] worldwide.…”

Section: B Multimode Video Transceiversmentioning

confidence: 99%

“…However, in order to counteract the problem of fast fading and co-channel interference, agile and tightspecification power-control algorithms are required [186]. Another technique that can be used to overcome the problems due to fading is adaptive-rate transmission [187], [188], where the information rate is varied according to the quality of the channel.…”

Section: B Jd-acdma Modem Mode Adaptation and Signalingmentioning

confidence: 99%

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Interactive cellular and cordless video telephony: State-of-the-art system design principles and expected performance

2000

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Second-generation (2G) mobile radio standards have not been designed with video communications in mind, although the employment of error-resilient, constant-bit-rate proprietary video codecs over these systems is realistic. The third-generation (3G) systems I. STATE-OF-THE-ART SYSTEM COMPONENT DEVELOPMENTS A. Introduction and OutlineThe subject of mobile radio communications has reached a state of maturity over the past two decades, as indicated by the excellent monographs by Jakes This contribution attempts to summarize a range of recent advances in the field of bandwidth-efficient wireless video communications. In this section, we commence our discourse with a brief overview of the wireless scene and, in particular, by considering the video transmission capabilities of the existing and future wireless systems. The geographical variation of the cellular channel capacity is characterized by Section II, as a motivation for invoking burst-by-burst adaptive transceivers [27]- [29]. The nature of co-channel interference (CCI)-which is the most dominant channel impairment in wireless systems-is the topic of Section III, where it is shown that the geographic variation of CCI justifies the employment of multimode transceivers, which are discussed in Section IV. Low-rate video compression aspects are reviewed in Section V, and the performance of the ITU H.263 codec is analyzed in some depth. Our discussions in Sections VI and VII are focused on the performance of reconfigurable video transceivers. Specifically, in Section VI, no power control is used-which is typically the case in cordless telephones, such as DECT and CT2-while in Section VII, power control is employed, which is characteristic of cellular systems, such as GSM [30], etc. Section VIII proposes a near-instantaneously adaptive or burst-by-burst adaptive code-division multiple-access (CDMA) scheme, which can be invoked in the context of the forthcoming 3G systems, in order to enhance their performance. Lastly, our discussions are concluded in Section IX with a range of system design guidelines. Let us now commence our overview of the range of existing and forthcoming wireless systems and their video transmission capabilities. B. Second-Generation (2G) Wireless SystemsThe existing 2G wireless systems now constitute a mature technology. Although they have not been designed with video communications in mind, with the advent of the specially designed error-resilient, fixed-rate video codecs [27]-[35] proposed by Streit et al., it is nonetheless realistic to provide videophone services over these low-rate schemes. For low-latency interactive videophony these systems have

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Section: B Multimode Video Transceiversmentioning

confidence: 99%

Section: B Jd-acdma Modem Mode Adaptation and Signalingmentioning

confidence: 99%

Interactive cellular and cordless video telephony: State-of-the-art system design principles and expected performance

2000

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“…Recent developments in AQAM over a narrow-band channel include contributions by Webb and Steele [1], Sampei et al [2], Torrance et al [3], and Goldsmith et al [4]. In these contributions the input SNR was used as the modem mode switching criterion which is not an adequate wide-band channel quality measure, where the transmission burst experiences both power fluctuations and intersymbol interference (ISI).…”

Section: Introductionmentioning

confidence: 99%

Upper-bound performance of a wide-band adaptive modem

Wong

Hanzo

2000

IEEE Trans. Commun.

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Abstract-Adaptive modulation is applied in conjunction with a decision-feedback equalizer (DFE) in order to mitigate the effects of the slowly varying wide-band multipath Rayleigh fading channel in a noise-limited environment. An upper-bound mean bit-error rate and bits per symbol performance is introduced for this scheme by utilizing the pseudo signal-to-noise ratio at the output of the DFE in order to switch the modulation schemes on a burst-by-burst basis.

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“…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%

“…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 (BER) can be maintained across a wide range of channel signal-to-noise ratios (SNRs) by adjusting the modulation mode between 1 and 6 bit/symbol (BPS) according to the instantaneous channel quality.…”

mentioning

confidence: 99%

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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Variable rate QAM for mobile radio

Cited by 375 publications

References 5 publications

Interactive cellular and cordless video telephony: State-of-the-art system design principles and expected performance

Interactive cellular and cordless video telephony: State-of-the-art system design principles and expected performance

Upper-bound performance of a wide-band adaptive modem

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

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