Abstract
The interference reduction capability of array antennas and the power control (PC) algorithms have been considered separately as means to increase the capacity in wireless communication networks. The capability of the smart antenna systems to track the user with the main lobe and interference with the nulls creates a significant impact on the current and future wireless sensor networks. In this paper, we use constrained least mean square (CLMS) and conjugate gradient adaptive beam-forming (CGBF) algorithms for narrowband adaptive beam-forming for tracking mobile user in a 2D urban environment without using PC algorithm. The CLMS algorithm is capable of efficiently adapting according to the environment and able to permanently maintain the chosen frequency response in the look direction while minimizing the output power of the array. In addition, with the CGBF algorithm, the desired users’ signal in an arbitrary path is passed and the inter-path interference (IPI) is canceled in other paths in each RAKE finger. The adaptability of the algorithms is closely observed for uniformly spaced linear array. Also in this paper, we present switched-beam (SB) technique. In the SB technique by using a number of fixed, independent, or directional antennas we increase the uplink capacity of the wireless systems. Simulation results indicate that the SB technique is able to considerably increase the signal to interference plus noise ratio (SINR) of mobile user in comparison with other algorithms. In addition, we observe that the SINR in the CLMS algorithm is lower than the CGBF algorithm. Finally, we discuss perfect power control and path loss parameter in urban environments and their effects on system capacity by simulations. Keywords: Antenna, Switched-beam, Power control, Urban signal propagation simulator, Wireless cellular network.
Highlights
The use of smart antennas is expected to have a dramatized in urban environments
With significant impact on future wireless communications to signal propagation simulator (USPS) software, mobile set meet the projected perspective of future communication antenna radiate beams which diffuse in all directions and networks
In condition that radiated user is called adaptive array processing. These systems beam is conflicted to an obstacle edge, diffraction are called adaptive beam-forming system and consist of phenomena is happened and diffracting point is diffusing spatially disposed sensor elements connected to a single channel or to a multi channel adaptive processor
Summary
The use of smart antennas is expected to have a dramatized in urban environments. with significant impact on future wireless communications to signal propagation simulator (USPS) software, mobile set meet the projected perspective of future communication antenna radiate beams which diffuse in all directions and networks. In Fig.[6] for 0.005 , d / 2 and N 10 , tracking mobile user for the CLMS algorithm in four positions (a, b and c, d are non-LoS and LoS positions, respectively) are shown as Fig.[5] According to this figure, by changing mobile user place, vectors for array components weights are arranged comparatively that considering produced beam pattern, difference between reference signal and received signal in output array antenna components is minimized. In Fig.[9], the SINR of mobile user in reverse link without power control algorithm versus the number of interference users (M-1) is compared In this simulation, we use the SB, CGBF, CLMS, and ES methods for N 15, 20 , d 0.5 , 0.75 , path loss parameter. The RLS method has more complexity in its structure than the CLMS method does
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