DocumentCode :
830966
Title :
Meeting mobile´s demands with multicarrier systems
Author :
Caldwell, Ryan ; Anpalagan, Alagan
Author_Institution :
Electr. Eng., Ryerson Univ., Canada
Volume :
24
Issue :
5
fYear :
2005
Firstpage :
27
Lastpage :
31
Abstract :
With the increasing requirements for future wireless applications, OFDM, MC-CDMA, and MC-DS-CDMA have all been considered for 4G wireless systems. These systems have the ability to incorporate very large band widths without sacrificing equalization complexity. The long symbol duration is effective at mitigating ISI, and adaptive modulation or frequency diversity can be used to provide protection against destructive fades. The benefit of MC CDMA is that it experiences frequency diversity because each bit is transmitted over several independently faded subcarriers. If some subcarriers experience destructive fades, diversity combining can be used at the receiver to recover the data. This improves the BER performance over OFDM, and this improvement is more significant as the number of subcarriers is increased. The draw back of MC-CDMA is that it may experience high levels of multiuser access interference (MAI) when the channel is heavily loaded. This occurs because each chip of the PN sequence experiences independent fading, which tends to destroy the orthogonality between spreading sequences. This increases the MAI and degrades the BER performance. Although OFDM, MC-CDMA, and MC-DS-CDMA signals experience a high PAPR, synchronization issues, and ICI, the benefits greatly outweigh these disadvantages.
Keywords :
4G mobile communication; OFDM modulation; adaptive modulation; code division multiple access; diversity reception; equalisers; error statistics; multiuser channels; pseudonoise codes; radio receivers; radiofrequency interference; sequences; spread spectrum communication; 4G wireless system; BER performance; ISI; MAI; MC-DS-CDMA; OFDM; PN sequence; adaptive modulation; equalization complexity; frequency diversity combining; mobile demand; multicarrier system; multiuser access interference; radio receiver; spreading sequence; symbol duration; synchronization issue; Bit error rate; Diversity reception; Frequency diversity; Frequency modulation; Intersymbol interference; Multiaccess communication; Multicarrier code division multiple access; Multiple access interference; OFDM modulation; Protection;
fLanguage :
English
Journal_Title :
Potentials, IEEE
Publisher :
ieee
ISSN :
0278-6648
Type :
jour
DOI :
10.1109/MP.2005.1594005
Filename :
1594005
Link To Document :
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