Title :
Multicarrier/QAM-level-controlled adaptive modulation for land mobile communication systems
Author :
Hamaguchi, Kiyoshi ; Moriyama, Eimatsu
Author_Institution :
Commun. Res. Lab., Minist. of Posts & Telecommun., Koganei, Japan
Abstract :
A multicarrier and an adaptive modulation combined system, where a suitable level of quadrature amplitude modulation (QAM) is selected for each carrier and time-slot using a QAM-level selection scheme, is proposed for digital land mobile communications. The advantages of the system are a mode in which information cannot be transmitted under adverse propagation conditions and a buffer memory to limit a transmission delay time. The QAM-level of each carrier is also controlled collectively according to the amount of the stored data bits in the memory. We confirmed the bit error rate (BER) performances of the system using computer simulation and we found that the system provided a noticeable BER improvement over frequency-selective fading channels and that the selection scheme was effective for a low maximum Doppler frequency and a small size of the memory
Keywords :
Doppler effect; adaptive systems; buffer storage; coding errors; delays; digital radio; error statistics; fading; land mobile radio; quadrature amplitude modulation; radiowave propagation; BER performance; QAM-level selection; QAM-level-controlled adaptive modulation; bit error rate; buffer memory; computer simulation; digital land mobile communications; frequency-selective fading channels; low maximum Doppler frequency; multicarrier modulation; propagation conditions; quadrature amplitude modulation; small memory size; stored data bits; transmission delay time; Adaptive systems; Amplitude modulation; Bit error rate; Communication system control; Computer simulation; Delay effects; Digital modulation; Mobile communication; Propagation delay; Quadrature amplitude modulation;
Conference_Titel :
Personal, Indoor and Mobile Radio Communications, 1997. Waves of the Year 2000. PIMRC '97., The 8th IEEE International Symposium on
Conference_Location :
Helsinki
Print_ISBN :
0-7803-3871-5
DOI :
10.1109/PIMRC.1997.627057