Lars Manholm

Non-line-of-sight small cell backhauling using microwave technology

In this article we discuss different technology alternatives for small cell backhaul, and we present high-frequency microwave technology as a very interesting alternative for wireless backhauling of small cells. In fact, we demonstrate that high-frequency microwave technology can be used for NLOS wireless backhauling of small cells, which opens up new applications for microwave technology. We discuss urban NLOS channel propagation at high frequencies, and we show both measurement and simulation results to validate the use of high-frequency microwave technology for NLOS small cell backhaul.

Analysis of an untilted wire-excited slot in the narrow wall of a rectangular waveguide by including the actual external structure

The admittance of an untilted slot in the narrow wall of a rectangular waveguide is calculated by including the actual external structure. The slot is excited by two tilted thin wires inside the waveguide. The slot is also allowed to extend into the two broad walls of the waveguide to make it sufficiently long for resonance to occur. The external slot admittance is evaluated by using a spectrum of two-dimensional solutions, a method which can handle the arbitrary cross section of the external structure, The analysis predicts that if both the slot and the wires are tuned to resonance, the transmission coefficient gets constant phase over a wide-frequency band. The results also show that resonance can be obtained for any slot length by adjusting the wire length, and this relation between the lengths is presented. The distance between the slot and the wires needed to maximize the radiated power is also shown; some results are confirmed by measurements.

MIMO Performance of Realistic UE Antennas in LTE Scenarios at 750 MHz

Multiple-input-multiple-output (MIMO) is a technique to achieve high data rates in mobile communication networks. Simulations are performed at both the antenna level and Long-Term Evolution (LTE) system level to assess the performance of realistic handheld devices with dual antennas at 750 MHz. It is shown that MIMO works very well and gives substantial performance gain in user devices with a quarter-wavelength antenna separation.

Non-Line-of-Sight Microwave Backhaul in Heterogeneous Networks

In this paper we present a study on the applicability and performance of microwave backhauling of small-cells in a heterogeneous network. Microwave backhaul in non-line-of-sight (NLOS) between a hub and a client provides a cost efficient and flexible small-cell deployment. In contrast to conventional NLOS communications using sub-6 GHz frequencies we propose the use of super-6 GHz frequencies which offers high antenna gain with reasonably sized antennas and wide bandwidths in licensed spectrum. We study both Point-to-Point (PtP) and Point-to-Multi-Point (PtMP) system concepts. The PtP system is characterized by pencil beam antennas with unshared radio resources for each link. The PtMP system is characterized by a single wide-beam antenna system at the hub with radio resources that are shared between multiple clients.

Practical multi-antenna terminals in LTE system performance simulations

In cellular radio network simulations the modeling of terminal antennas is often extremely simplified. In this paper the results from a study on the impact of using realistic terminal antennas in LTE system simulations are presented. Results from downlink simulations using measured radiation patterns of a number of typical multi-antenna terminals have been compared with results using an ideal antenna model. The results showed that the impact was weak in a scenario with high intercell interference while a substantial performance degradation could be observed in a scenario with low interference. Cell-edge throughput was found to be the most sensitive performance metric which in the worst case suffered a 53% throughput reduction compared to the ideal model. An analysis of the relation between antenna properties and system performance is also presented. It was observed that the geometric mean of the eigenvalues of the pattern covariance matrix has a distinct connection to system performance. It was also found that efficiency is important for cell-edge throughput and that the pattern correlation has impact on peak throughput.

Dual beam phased array antenna with wide scan angle for repeater applications

A dual polarized, dual beam phased array antenna with wide scan angle capabilities was designed and manufactured for repeater application. Two fixed feeding networks were designed and manufactured for the dual beams. With the feed networks, one broadside main beam and one tilted main beam were generated. The antenna achieved good isolation of -35.5 dB between the two main beams (broadside and tilted beam) within the frequency band of interest (2.5-2.7 GHz). The return loss for the broadside feed network port was found to be below -7.5 dB and return loss for the tilted beam feed network port was less than -15 dB. The side lobe levels for the broadside beam and the tilted beam were -12 dB and -8 dB down, respectively. The cross-polar level for the broadside beam was lower than -20 dB at the center frequency both in the elevation plane and in the azimuth plane. Also, for the tilted beam the cross-polar level in elevation plane was measured to be as low as -20 dB at the centre frequency.