21,718 research outputs found
Invertible bounds for M-QAM in Rayleigh fading
No full textIn this letter, we derive tight invertible bounds on the bit-error probability (BEP) for the coherent detection of M-ary quadrature amplitude modulation with Gray code bit mapping in Rayleigh fading channels. These bounds enable us to easily obtain tight lower and upper bounds on the bit-error outage (BEO), i.e., BEP-based outage probability, in a log-normal shadowing environment. As examples of applications, these bounds are used to investigate the BEO and mean spectral efficiency for slow adaptive modulation
Multi-channel reception for slow adaptive M-QAM in fading channels
No full textIn this letter we investigate the performance of slow adaptive M -ary quadrature amplitude modu-
lation with coherent multichannel reception. We consider a slow adaptive modulation (SAM) technique
which adapts the constellation size to the slow variation of the channel due, for example, to shadowing.
The proposed SAM technique is more practical than conventional adaptive modulation techniques that
require the adaptation to fast fading variations. Our results show that SAM technique can provide
substantial increase in throughput while maintaining an acceptable low bit error outage
On the performance of slow adaptive M-QAM with antenna subset diversity in fading channels
No full textIn this paper, we investigate the performance of adaptive M-ary quadrature amplitude modulation with antenna subset diversity. We consider a slow adaptive modulation (SAM) technique which adapts the constellation size to the slow variation of the channel due, for example, to shadowing. Our results show that the SAM technique can provide substantial increase in throughput with respect to fixed schemes while maintaining an acceptable low bit error outage. We also compare SAM with a fast adaptive modulation (FAM) technique, which tracks fast fading variations, showing that the throughput of SAM is close to that of FAM despite the fact that SAM is less complex and requires a lower feedback rate to the transmitter
Slow adaptive M-QAM with diversity in fast fading and shadowing
No full textThis paper investigates the performance of adaptive M-ary quadrature amplitude modulation (QAM) with antenna subset diversity. We consider a slow adaptive modulation (SAM) technique that adapts the constellation size to the slow variation of the channel due, for example, to shadowing. The proposed SAM technique is more practical than conventional fast adaptive modulation (FAM) techniques that require adaptation to fast-fading variations. Our results show that the SAM technique can provide a substantial increase in throughput with respect to fixed schemes while maintaining an acceptable low bit-error outage. We also compare SAM and FAM techniques, showing that the throughput of SAM can be, in many practical cases, close to that of FAM, despite the fact that SAM is less complex and requires a lower feedback rate. For example, using a set of possible modulations {4,16,64}-QAM with dual-branch maximal ratio combining reception, 5% outage at a bit-error probability of 10-2 and a median signal-to-noise ratio of 22 dB, SAM is capable of improving the mean spectral efficiency of fixed schemes from about 1.9 to 4.7 b/s/Hz, which is close to the 5.5 b/s/Hz achieved by FA
Tight bounds on outage and throughput for M-QAM in fading channels
No full textIn this paper, we firstly derive tight invertible bounds on the bit error probability (BEP) for coherent detection of M-QAM in Rayleigh fading channels. These bounds enable us to easily obtain tight lower and upper bounds on the bit error outage (BEO). As examples of applications, these bounds are used to investigate the BEO in a log-normal shadowing environment. Moreover, using the bounds on the inverse BEP, the analysis of the mean spectral efficiency for slow adaptive modulation is assessed
On the inverse symbol-error probability for diversity reception
No full textThis paper addresses the problem of finding the inverse symbol-error probability (SEP) expression for coherent detection of M-ary phase-shift keying with multichannel reception and maximal ratio combining in Rayleigh fading. To this aim, we derive upper and lower bounds on SEP that are simply invertible and uniformly tight for all values of signal-to-noise ratio. This enables us to obtain tight bounds on the inverse SEP and on the symbol-error outage (SEO), i.e., SEP-based outage probability. As an example of application to digital mobile radio, the SEO in a log-normal shadowing environment is analyzed
On the performance of slow adaptive M-QAM with antenna subset diversity in fading channels
No full textmmWave Communications for High Mobility Devices: The Case of Road Side Links
No full textMobile communication at millimeter-waves (mmWaves) is affected by the rapid and random variations of the wireless environment. This requires accurate channel estimation at the receiver to compensate for the channel dynamics. The required channel training overhead has been shown to occupy a considerable fraction of the mmWave transmission bandwidth, especially when the mobile device (MD) moves at high-speed. We cope with the issue of the rapid variation of the channel by introducing a coherent transmission/detection technique, whose mechanism requires that MD has prior knowledge of its position as an alternative to the channel estimate. In particular, we consider the case of road side links with high-speed MDs and derive a closed-form expression for the optimal detector. We show that the proposed approach reduces the training overhead significantly at the expense of a signal-to-noise ratio (SNR) increase for a given bit error rate
A new class of tight and invertible bounds on the sep for diversity reception
No full textA class of invertible and uniformly tight upper and lower bounds was derived for coherent detection of phase shift keying (PSK) with multichannel reception. The derived bounds were calculated such that they were tight for all values of signal to noise ratios (SNR). The difference between upper and lower bound was compared with those obtained from optimized simple bounds to investigate the tightness of the bounds
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