Spectrum Is a Limied and Valuable Resource

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Spectrum is a limited and valuable resource. The escalating requirement for wireless communication and broadband services has augmented the attempts to improve the designs for wireless systems. These enhanced wireless systems offer substantial increase in data throughput and link range without the requirement of any additional bandwidth. This led to the development of MIMO Systems. In Multiple-Input Multiple-Output (MIMO) technology, multiple antennas are used at both the transmitter and receiver to improve the functioning of the wireless communication system. We accomplish this objective by exploiting the spatial domain of the transmission medium. In this chapter, we describe the MIMO system model along with a brief discussion of its operation principle is detail in section 3.2. In Section 3.3, we have discussed MIMO channel models, and the basic parameters influencing the MIMO system design. Narrowband and wideband MIMO channels which are part of this thesis are also discussed in this section only. Section 3.4 enumerates spatial correlation, an impairment specific to MIMO systems worth considering while designing MIMO systems. 3.2 MIMO Communication Model: Multiple-Input Multiple-Output (MIMO) technology is the foundation of new-age wireless communication systems due to the budding data rate and improved performance of wireless links. These qualities are offered due to the transmission diversity. The transmitting antennas and the receiving antennas are linked such that the quality (the bit error rate (BER), or the data rate) for each user is improved. The viability of implementing MIMO system and the associated signal processing algorithms increases with an equal and corresponding increase in the computational power of the int... ... middle of paper ... ... kept at both the sides of the wireless link, representing as single-input/single output (SISO) system. Employing multiple antennas on either sides of the communication link, system is represented as multiple input/multiple output (MIMO) systems [Tarokh 1998]. This dissimilarity in a SISO system and a MIMO system using Nt transmitting and NR receiving antennas is the means of representing a single stream of data symbols to Nt streams of symbols and the equivalent inverse operation at the receiver side. Systems with multiple antennas on the receiver side only are called single input/multiple output (SIMO) systems whereas with multiple antennas at the transmitter side only are called multiple input/single output (MISO) systems. The MIMO system is the most frequently used and it includes SISO, MISO, and SIMO systems as special cases which are shown below in figure 3.3:

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