Abstract
Hierarchical constellations constitute a simple technique for achieving multiresolution and, therefore, are appealing for MBMS (Multimedia Broadcast and Multicast Service). In this paper we consider the use of M-QAM hierarchical constellations (Quadrature Amplitude Modulation) combined with MIMO (Multiple Input Multiple Output) for the transmission of multicast and broadcast services in UTRA (Universal Mobile Telecommunications System Terrestrial Radio Access) Long Term Evolution (LTE) systems based on Orthogonal Frequency Division Multiplexing (OFDM). Due to the demanding channel estimation requirements and the high sensitivity to interference resulting from the usage of several antennas and hierarchical constellations, an enhanced receiver based on the turbo concept is employed and its performance is evaluated.
Highlights
It is widely recognized that Orthogonal Frequency Division Multiplexing (OFDM) modulations [1] are suitable for broadband wireless systems
Regarding UTRA Long Term Evolution (LTE), special attention is being devoted to the support of MBMS which has already been standardized in 3GPP UTRAN (UMTS Terrestrial Radio Access Network) Release-6 [4] and 7 [5]
In this paper we consider the use of QAM hierarchical constellations in a UTRA LTE OFDM based system employing multiple transmitting and receiving antennas with the aim of supporting broadcast and multicast services
Summary
It is widely recognized that OFDM modulations [1] are suitable for broadband wireless systems. By having several classes of bits with different error protection associated and to which different streams of information are mapped, a given user can attempt to demodulate only the more protected bits or the bits that carry the additional information, depending on the propagation conditions This type of approach is possible whenever the information can be scalable like the cases of coded voice or video signals, as studied in [6][7]. In this paper we consider the use of QAM hierarchical constellations in a UTRA LTE OFDM based system employing multiple transmitting and receiving antennas with the aim of supporting broadcast and multicast services. To deal with the high sensitivity to channel estimation errors we employ an iterative receiver capable of performing joint MIMO detection and channel estimation This receiver is based on the approach proposed in [11] for WCDMA systems.
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