An adaptive array for mobile communication systems

A Review on Importance of Improving Spectral Efficiency in Massive MIMO Communications

“…There are many reasons why multi-user MIMO is the most scalable and attractive solution [17]. Firstly, the wavelength is 5-30 cm in the frequency range of cellular communication (1)(2)(3)(4)(5)(6). This limits the number of antennas that can be deployed in a compact user terminal for point-to-point MIMO, while one can have almost any number of spatially separated single-antenna terminals in multi-user MIMO.…”

“…Some notable early works are the array processing papers [1,38,44,47], the patent [36] on spatial division multiple access (SDMA), and the seminal information-theoretic works [11,18,42,43,46] that characterized the achievable multi-user capacity regions, assuming that perfect channel state information (CSI) is available in the system. In this section, we summarize some of the main design insights that have been obtained over the years.…”

Adaptive interference suppression in multiuser wireless OFDM systems using antenna arrays

“…Another key advantage of DOA-based beamforming is that since DOA information is independent of carrier frequency, the information can be reused for downlink beamforming as well. See [1], [6], [9], [13], and [24] for DOA estimation algorithms employed to estimate and track directions of desired and interfering signals specifically in mobile radio environments. In addition to conventional algorithms, DOA estimation techniques based on time-differenceof-arrival and multiple base station triangulation are also emerging [17], and the resulting information can also be utilized for other tasks such as mobile handoffs and geolocation.…”

“…In the absence of channel and implementation imperfections, each subchannel in an OFDM signal is exactly orthogonal to all other subchannels. 1 However, timeselective fading diminishes interchannel orthogonality and leads to mutual interference between data-carrying OFDM subchannels, referred to as interchannel interference (ICI). Another major source of ICI is frequency offsets due to imperfect transceiver synchronization and phase noise.…”

Microstrip Patch Antenna Assisted Compact Dual Band Planar Crossover

“…In this, the switched beam antenna can be realized easily at low cost in comparison with an adaptive antenna array. A switched beam antenna requires radiating elements, a beamforming network and Radio Frequency (RF) switches [6] while adaptive array systems are much more complex, requiring advanced signal processing [7] techniques. Butler matrix is one of the common method used in switched beam system has 90 • hybrid coupler, delay lines and crossover associated with it [8].…”